I have changed my css sheet for my entire site and it works great. The change has to do with the background color of rows in tables. Although it does what I want, there is one view that I would like to be exempt from this alteration. Is there a way to exclude this view from the change or create a new css sheet for this specific view?
Well, I would come up with a CSS styling strategy. The goal should be to minimize CSS and overrides. Also, having an extra CSS file for just one page will cause an extra HTTP round trip to get the resource. My recommendation is to stick extra CSS classes on this view. Then, override precisely the styles that you need in your global CSS styles.
I figured out the solution which ended up being much easier than I expected. Since I am very new to using CSS and HTML I was unaware of the style tag. However, that is what I was looking for. For anybody looking at this in the future, just use:
<style>
(CSS that you would like to override)
</style>
I have a simple HTML page that is referencing 3 CSS files. The first is a style sheet that is just for the page. The other two are for the styles of two unique modals. These modal CSS files were not created by me and they are happily being used separately on other pages throughout the site.
My problem is that both of these modal CSS files contain a few common selectors and so they are messing up each other's styles.
I understand that the best way to fix this problem is to take one or both of the files and make their selectors unique. One way would be to namespace the selectors.
My questions is, however, now that I'm knee-deep in this page, is there anyway to prevent these CSS conflicts without changing the modal CSS pages as they currently stand? Are there any tools that can help such as LESS? What is the best practice for preventing this in the future?
The best solution indeed would be to refactor those css-files to your need.
However, an easier solution would be to include your stylesheet after those two third-party css-files and re-declare the styles for the common selectors, which automatically overrides the previous settings.
LESS/SASS are excellent tools to help you write CSS faster and more comfortable. I use SASS for private work and really recommend it. They can't help you though with issues like you have atm.
EDIT:
Using !important is possible, but considered bad habit, as it was intended to give the user the possibility to override author-styles with his own. Instead of using !important what you should do is:
Avoid duplicate styles as much as you can.
if you can't avoid this, try to resolve this by either:
cascading (=using the proper sequence to override previous styles)
using selector specificity (W3C-Spec).
Assuming:
...
<link rel="stylesheet" href="this_page.css" />
<link rel="stylesheet" href="modal_1.css" />
<link rel="stylesheet" href="modal_2.css" />
...
Due to the cascading nature of CSS (sorry, I had to) using the same selector over and over overrides any previous styles. Thus, if modal_1.css and modal_2.css both apply style x to the body tag, for example, the second stylesheet will override the first.
The sad part is that there is no way out other than to, as you suggested, modify the two selectors to make them more specific.
Looking to the future, the best way to avoid overriding previously declared styles, is to always be specific about the particular element you are targeting, and it's proper place in the DOM. Note that LESS is simply a CSS preprocessor, which only allows you a different syntax for CSS.
I would suggest to a common class add into body tag of that particular page & target using that particular class. If you tools like LESS or Compass you can easily achieve the aim.
.pageOne{ /*All the styles for this perticular page*/
.header{
}
.sidebar{
}
}
When parse through LESS or Compass it will look like following.
.pageOne .header{}
.pageOne .sidebar{}
This way your page will get a namespace.
I am injecting some html + css into every page from my firefox plugin. But this styles is sometimes getting overridden by the style sheet. I want to stop this behavior.
I know this can be solved by some css tricks. Adding !important for instance. But is there a way available in firefox or xul to do this easily?
Using !important alone is not enough, the webpage could do the same and still override your styls. You can use the Stylesheet Service to register a user stylesheet. If you then use !important then web pages will no longer be able to override your styles.
Note that user stylesheets are always global and apply to all webpages as well as browser's own XUL documents. You can restrict them to particular webpages using #-moz-document.
#MEGA_PLUNGIN a {}
#MEGA_PLUNGIN span {}
#MEGA_PLUNGIN div {}
#MEGA_PLUNGIN table {}
...
Not the best solution but right...
To me, this is one case where you would certainly use !important.
That said, you can try to use specificity to ensure your styles are being set.
So, make sure that you are targeting the elements are precisely as possible, in order to override those styles that are not as specific.
For instance, if you have this structure
<body>
<div>
<h1 class="something">
<a href>
The site's styles may target
h1.something a{
You should aim to do this
body div h1.something a{
which is more specific and would override the above styles.
The other thing you might be able to do is append your styles just before the </head>, which would make them appear last in the cascade, and, if they are equal, will be applied.
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.