After looking through everything except the Gecko source, I'm somewhat confused by the following behavior. I wanted to see if I could style a text input based on a user-inputted value, and eventually ended up with this CSS:
input[value="password"] {
border:1px solid red;
}
The problem is, it seems the value of an input is only checked on the elements creation, as seen in this example.
Is it possible to accomplish this without the use of Javascript? Why would a browser not update styles accordingly?
It doesn’t work, because attribute selectors “match elements which have certain attributes defined in the source document” (Attribute selectors in CSS 2.1). Things are a bit more complicated really, because calling setAttribute('value','password') on the input element causes a match in many browsers (not IE). But this is irrelevant if you don’t use JavaScript.
There is, however, an indirect way, though it is mostly theoretical for the time being, due to limited browser support and to complications in implementations. You could write:
<style>
input:valid { border: 1px solid red; }
</style>
<input pattern=password id=x>
This uses the HTML5 pattern attribute, in this case specifying a regular expression that is merely a fixed string with no wildcards, and the CSS3 Basic UI :valid pseudo-class that tests whether the element’s state satisfies validity constraints. This is not suitable for normal use (e.g., no support in IE 9), but in special situations in controlled environments, things like this might be usable.
However, browsers that support such features tend to have their own reporting of validity errors, like special color around the box when the value is invalid, and I don’t think you can change that in CSS – JavaScript might help, but… So the reporting might conflict with your goals here. Moreover, it seems that browsers supporting these features treat the element’s state as valid when the box is empty. This is odd, and attempts to work around this my making the input obligatory (HTML5 attribute required) seem to open new cans of worms rather than fix. But maybe in some cases you could use just some initial value, say value="?", that the user is expected to replace by this input.
No. CSS cannot check the value of an input field past what is available in the HTML structure.
When you're typing into an input field, you're not actually changing the attribute in the HTML.
This does not work because you're not actually changing the value attribute of the element. For example, look at this fiddle:
http://jsfiddle.net/jblasco/J9xSd/
It does work, because the value attribute is actually changed. Simply typing in the field, or updating it through the Javascript method you used, does not change it. Which is normally useful, for getting the default value later, but perhaps not-so-useful in this sense.
I have a table, with 10 columns. I want to control the width of each column.
Each column is unique, right now I create an external CSS style for each column:
div#my-page table#members th.name-col
{ width: 40px; }
I know there is a best practice to avoid inline style.
I do approve using external CSS for anything look'n'feel related: fonts, colors, images.
But is it really better to use external CSS in this case?
It does not incur extra maintenance cost.
It is easier to produce.
Cons I can think of:
If you have separate designers and development team - using inline styles will force designers to modify content-file (aspx in my case).
It might use more bandwidth.
Anything else I've missed?
IMPORTANT: I am asking about only one specific case where style used will ever apply to exactly one element, and is not part of the global-theme, such as width of one particular column.
There are lots of reasons why style="" is bad. I consider it a bug anywhere I encounter it in my codebase. Here are some reasons:
style= has higher priority than other CSS selectors making it hard to effect changes in the stylesheet; the stylesheet has to work harder to override these.
style= rules are hard to find in the code when you need to make global changes.
You download this CSS code with every page view.
If you have multiple stylesheets for the same HTML codebase your style= rules are not part of the stylesheet and thus are unchangeable.
However, if you are generating content and it's difficult to describe this content in a static CSS file, you might also need to generate the CSS to match that content. It is often easier to simply generate style= rules despite the drawbacks. If, however, your generated content can be easily described in a CSS file, because the generated structure doesn't often change, or because you can easily generate HTML AND a CSS file at the same time, then it's probably better to not use style=.
Some suggestions for alternatives to style= that may be appropriate:
Instead of inline styles, use class names. Works well if you have lots of columns in your table that have the same properties, and which you expect to always have the same properties. Then your stylesheet can remain fixed while your HTML is fluid, since the CSS only references classes. This is probably the approach I'd use.
Use JQuery or some other javascript library to style your objects programmatically after the page loads.
Easier to produce is not really a valid argument - people like splitting huge chunks of code into smaller chunks - same with code and markup.
However:
+ No extra HTTP connection (unless you are already downloading a .css file anyway)
- Every time the page gets sent, this CSS is sent with => more bandwith
- Designers need to modify CSS in Application Code (bad practice)
Usually, you shouldn't - unless it's a really well thought through performance tweak as google does.
When I see website starter code and examples, the CSS is always in a separate file, named something like "main.css", "default.css", or "Site.css". However, when I'm coding up a page, I'm often tempted to throw the CSS in-line with a DOM element, such as by setting "float: right" on an image. I get the feeling that this is "bad coding", since it's so rarely done in examples.
I understand that if the style will be applied to multiple objects, it's wise to follow "Don't Repeat Yourself" (DRY) and assign it to a CSS class to be referenced by each element. However, if I won't be repeating the CSS on another element, why not in-line the CSS as I write the HTML?
The question: Is using in-line CSS considered bad, even if it will only be used on that element? If so, why?
Example (is this bad?):
<img src="myimage.gif" style="float:right" />
Having to change 100 lines of code when you want to make the site look different. That may not apply in your example, but if you're using inline css for things like
<div style ="font-size:larger; text-align:center; font-weight:bold">
on each page to denote a page header, it would be a lot easier to maintain as
<div class="pageheader">
if the pageheader is defined in a single stylesheet so that if you want to change how a page header looks across the entire site, you change the css in one place.
However, I'll be a heretic and say that in your example, I see no problem. You're targeting the behavior of a single image, which probably has to look right on a single page, so putting the actual css in a stylesheet would probably be overkill.
The advantage for having a different css file are
Easy to maintain your html page
Change to the Look and feel will be easy and you can have support for many themes on your pages.
Your css file will be cached on the browser side. So you will contribute a little on internet traffic by not loading some kbs of data every time a the page is refreshed or user navigates your site.
The html5 approach to fast css prototyping
or: <style> tags are no longer just for the head any more!
Hacking CSS
Let's say you're debugging, and want to modify your page-css, make a certain section only look better. Instead of creating your styles inline the quick and dirty and un-maintainable way, you can do what I do these days and take a staged approach.
No inline style attribute
Never create your css inline, by which I mean: <element style='color:red'> or even <img style='float:right'> It's very convenient, but doesn't reflect actual selector specificity in a real css file later, and if you keep it, you'll regret the maintenance load later.
Prototype with <style> instead
Where you would have used inline css, instead use in-page <style> elements. Try that out! It works fine in all browsers, so is great for testing, yet allows you to gracefully move such css out to your global css files whenever you want/need to! ( *just be aware that the selectors will only have page-level specificity, instead of site-level specificity, so be wary of being too general) Just as clean as in your css files:
<style>
.avatar-image{
float:right
}
.faq .warning{
color:crimson;
}
p{
border-left:thin medium blue;
// this general of a selector would be very bad, though.
// so be aware of what'll happen to general selectors if they go
// global
}
</style>
Refactoring other people's inline css
Sometimes you're not even the problem, and you're dealing with someone else's inline css, and you have to refactor it. This is another great use for the <style> in page, so that you can directly strip the inline css and immediate place it right on the page in classes or ids or selectors while you're refactoring. If you are careful enough with your selectors as you go, you can then move the final result to the global css file at the end with just a copy & paste.
It's a little hard to transfer every bit of css immediately to the global css file, but with in-page <style> elements, we now have alternatives.
In addition to other answers.... Internationalization.
Depending of the language of the content - you often need to adapt the styling of an element.
One obvious example would be right-to-left languages.
Let's say you used your code:
<img src="myimage.gif" style="float:right" />
Now say you want your website to support rtl languages - you would need:
<img src="myimage.gif" style="float:left" />
So now, if you want to support both languages, there's no way to assign a value to float using inline styling.
With CSS this is easily taken care of with the lang attribute
So you could do something like this:
img {
float:right;
}
html[lang="he"] img { /* Hebrew. or.. lang="ar" for Arabic etc */
float:left;
}
Demo
Inline CSS will always, always win in precedence over any linked-stylesheet CSS. This can cause enormous headache for you if and when you go and write a proper cascading stylesheet, and your properties aren't applying correctly.
It also hurts your application semantically: CSS is about separating presentation from markup. When you tangle the two together, things get much more difficult to understand and maintain. It's a similar principle as separating database code from your controller code on the server side of things.
Finally, imagine that you have 20 of those image tags. What happens when you decide that they should be floated left?
This only applies to handwritten code. If you generate code, I think that it's okay to use inline styles here and then, especially in cases where elements and controls need special treatment.
DRY is a good concept for handwritten code, but in machine-generated code, I opt for "Law of Demeter": "What belongs together, must stay together". It's easier to manipulate code that generates Style tags than to edit a global style a second time in a different and "remote" CSS file.
The answer to your question: it depends...
Using inline CSS is much harder to maintain.
For every property you want to change, using inline CSS requires you to look for the corresponding HTML code, instead of just looking inside clearly-defined and hopefully well-structured CSS files.
The whole point of CSS is to separate content from its presentation. So in your example you are mixing content with presentation and this may be "considered harmful".
In addition to the other answers, another concern is that it violates the recommended Content Security Policy from MDN, https://infosec.mozilla.org/guidelines/web_security#content-security-policy
The justification they use is that inline javascript is harmful, XSS, etc., but it doesn't justify why inline styles should also be disabled. Maybe someone can comment as to why, but until then, I'll just rely on appeal-to-authority and claim: it's a security best practice to avoid inline styles.
Code how you like to code, but if you are passing it on to someone else it is best to use what everyone else does. There are reasons for CSS, then there are reasons for inline. I use both, because it is just easier for me. Using CSS is wonderful when you have a lot of the same repetition. However, when you have a bunch of different elements with different properties then that becomes a problem. One instance for me is when I am positioning elements on a page. Each element as a different top and left property. If I put that all in a CSS that would really annoy the mess out of me going between the html and css page. So CSS is great when you want everything to have the same font, color, hover effect, etc. But when everything has a different position adding a CSS instance for each element can really be a pain. That is just my opinion though. CSS really has great relevance in larger applications when your having to dig through code. Use Mozilla web developer plugin and it will help you find the elements IDs and Classes.
I think that even if you want to have a certain style for one element, you have to consider the possibility that you may want to apply the same style on the same element on different pages.
One day somebody may ask to change or add more stylistic changes to the same element on every page. If you had the styles defined in an external CSS file, you would only have to make changes there, and it would be reflected in the same element in all of the pages, thus saving you a headache. :-)
Even if you only use the style once as in this example you've still mixed CONTENT and DESIGN. Lookup "Separation of concerns".
Using inline styles violates the Separation of Concerns principle, as you are effectively mixing markup and style in the same source file. It also, in most cases, violates the DRY (Don't Repeat Yourself) principle since they are only applicable to a single element, whereas a class can be applied to several of them (and even be extended through the magic of CSS rules!).
Furthermore, judicious use of classes is beneficial if your site contains scripting. For example, several popular JavaScript libs such as JQuery depend heavily on classes as selectors.
Finally, using classes adds additional clarity to your DOM, since you effectively have descriptors telling you what kind of element a given node in it is. For example:
<div class="header-row">It's a row!</div>
Is a lot more expressive than:
<div style="height: 80px; width: 100%;">It's...something?</div>
Inline CSS is good for machine-generated code, and can be fine when most visitors only browse one page on a site, but one thing it can't do is handle media queries to allow different looks for screens of different sizes. For that, you need to include the CSS either in an external style sheet or in an internal style tag.
In-page css is the in-thing at the moment because Google rates it as giving a better user experience than css loaded from a separate file. A possible solution is to put the css in a text file, load it on the fly with php, and output it into the document head. In the <head> section include this:
<head> ...
<?php
$codestring = file_get_contents("styles/style1.txt");
echo "<style>" . $codestring . "</style>";
?>
... </head>
Put the required css in styles/style1.txt and it'll get spat out in the <head> section of your document. This way, you'll have in-page css with the benefit of using a style template, style1.txt, which can be shared by any and all pages, allowing site-wide style changes to be made via only that one file. Furthermore, this method doesn't require the browser to request separate css files from the server (thus minimising retrieval / rendering time), since everything is delivered at once by php.
Having implemented this, individual one-time-only styles can be manually coded where needed.
According to the AMP HTML Specification it is necessary to put CSS in your HTML file (vs an external stylesheet) for performance purposes. This does not mean inline CSS but they do specify no external stylesheets.
An incomplete list of optimizations such a serving system might do is:
Replace image references with images sized to the viewer’s viewport.
Inline images that are visible above the fold.
Inline CSS variables.
Preload extended components.
Minify HTML and CSS.
Personally, I think the hatred of inline css is just ridiculous. Hardcore cult behaviour, people just sheepishly repeat "Separation of concerns!". Yes, there are times where if there is a repeating element and you will need repeated styling to use a class targeted from a CSS file, but most of the time it improves speed of development and CLARITY OF CODE to put the style inline, it's great if I can look at the code and see that there is a custom margin height, it helps me picture the HTML document as a whole, instead of some named class that gives me little insight into which styles will be applied.
So I will be the contrarian here and say that inline css is great and that people who scream at you for using it are just following what they have been told without actually giving it any original unbiased consideration.
Even though I totally agree with all the answers given above that writing CSS in a separate file is always better from code reusability, maintainability, better separation of concerns there are many scenarios where people prefer inline CSS in their production code -
The external CSS file causes one extra HTTP call to browser and thus additional latency. Instead if the CSS is inserted inline then browser can start parsing it right away. Especially over SSL HTTP calls are more costly and adds up additional latency to the page. There are many tools available that helps to generate static HTML pages (or page snippet) by inserting external CSS files as inline code. These tools are used at the Build and Release phase where the production binary is generated. This way we get all the advantages of external CSS and also the page becomes faster.
In addition to other answers, you cant target the pseudo-classes or pseudo-elements in inline CSS
We have created a template-driven artifact generator that provides an include file capability for any kind of text artifact -- HTML, XML, computer languages, unstructured text, DSV, etc. (E.g., it's great for handling common Web or manual page headers and footers without scripting.)
Once you have that and use it to provide "style" tags inside your "head" tag, the "separation of concerns" argument goes away, to be replaced by "we have to regenerate after every change to the template" and "we have to debug the template from what it generates". Those gripes have been around since the first computer language to get a preprocessor (or someone started using M4).
On balance, we think the meta-izing capability of either a CSS file or "style" tags is cleaner and less error-prone than element-level styling. But it does require some professional judgment, so newbies and scatterbrains don't bother.
Is it only for screen reader software? because browser renders both type of tags semantic and presentational in same manner.
For example:
for browser for us and for css <strong> and <b> is same. what is the purpose to semantic tag over presentational tag.
is it for screen readers only or it's for better management of code?
if it's for developer strong and b both can produce same result on browser.
Semantic markup allows scripts to understand context. This may be beneficial for screen reader software, but it will also be beneficial for Google and other search bots.
According to HTML specs, <strong> and <em> communicate emphasis, whereas <b> and <i> simply mean "display bold" and "display italic". <b> and <i> should be used in instances where emphasis is specifically not desired. For example, when italicizing a book title.
When search bots are trying to gain semantic understanding of content, it is reasonable to assume they give greater preference to semantic tags.
<strong> and <b> is a poor example in this case, as they are just historically used in a wrong notion. A lot of people started marking everything bold with <strong>, thus destroying the original intent. My phone browser does not make <strong> bold for instance (although the standards suggests making it bolder on screen).
The idea behind semantic tags is to provide some description about the content. So <strong> tag for menu items does not make any sense, while it makes sense to use it to mark part of a sentence as if it was pronounced louder.
With HTML5 semantic tags make a lot more sense, because the content part of the page is clearly outlined, and every tag inside the content is a usable meta data. Search engines are already good at this, but everyone else isn't.
I suggest reading about the whole concept of Semantic Web.
In theory, an audio page reader could read <strong> text in a different, slower, more emphasized tone of voice. It wouldn't do that for just <b> because that's only a typographical hint for graphical presentation. A terminal-based browser could use underlining to reproduce <strong> as an alternative to bold if it's not an available effect on the terminal, where is principle it wouldn't make sense to do that for typographical <b>. A search engine could give more importance to <strong>ed words.
In practice, I don't think any of these examples actually happen — partly, as HeavyWave says, because decades of poor-quality markup have erased any difference between them that could usefully be drawn — but it demonstrates the philosophical difference.
4.2. Element and attribute names must be in lower case
XHTML documents must use lower case for all HTML element and attribute names. This difference is necessary because XML is case-sensitive e.g. <li> and <LI> are different tags.
Source : http://www.w3.org/TR/2002/REC-xhtml1-20020801/diffs.html#h-4.2
But is it also necessary for attributes, properties, values, class and ID for elements.
Upper case and came case should not be used.
What is the benefit of use lowercase for every thing?
What is the benefit of use lowercase for every thing?
There are a few good reasons:
simplifies implementation; you'll only have to look for one variant to match a tag, not all its case-sensitive variants, for example
easier to type, if needed; humans appreciate things that save them effort
one consistent way to do everything
lower cognitive overhead about whether this tag should be capitalized or not
The only real benefit is that your webpage will be XHTML compliant. Browsers are built on the philosophy of "Be conservative in what you emit and liberal in what you accept", and doing crazy capitalization things should not throw any of them (except maybe IE, but that's a whole other battle)
As for theoretical benefits, it saves time/effort for developers, but AFAIK, browsers don't care, so...