What does appending a query string to the end of a style sheet do? I often see:
some-stylesheet.css?ver=1.2.3
Thanks.
Usually people use it to prevent caching of the CSS file.
It could also be used by the server software (Apache, for example) to load a specific version of the CSS based on the string.
Adding a new query string forces the browser to reload the file instead of using a cached one.
it helps with caching, if you append a query string the browser treats it like a new file, that way when you make changes they are shown immediately, not after you clear the browser cache
This is used in order to workaround browser caching while developing. If you increment that number in your HTML, browser will suppose it's a new file that he has not see ever before and will render the last version of it.
Problably they want to show you the newest version of the CSS, without caché of the browser. So using a parameter its solved.
Related
I noticed some websites put the version numbers (especially) in the CSS file path. For example:
<link rel="stylesheet" type="text/css" href="style.css?v=12345678" />
What is the main purpose to put the version number? If the purpose is to remember when the CSS file was updated last time, shouldn't the version number added as a comment inside the CSS file?
From HTML5 ★ Boilerplate Docs:
What is ?v=1" '?v=1' is the JavaScript/CSS Version Control with
Cachebusting
Why do you need to cache JavaScript CSS? Web page designs are getting
richer and richer, which means more scripts and stylesheets in the
page. A first-time visitor to your page may have to make several HTTP
requests, but by using the Expires header you make those components
cacheable. This avoids unnecessary HTTP requests on subsequent page
views. Expires headers are most often used with images, but they
should be used on all components including scripts, stylesheets etc.
How does HTML5 Boilerplate handle JavaScript CSS cache? HTML5
Boilerplate comes with server configuration files: .htacess,
web.config and nginx.conf. These files tell the server to add
JavaScript CSS cache control.
When do you need to use version control with cachebusting?
Traditionally, if you use a far future Expires header you have to
change the component's filename whenever the component changes.
How to use cachebusting? If you update your JavaScript or CSS, just
update the "?v=1" to "?v=2", "?v=3" ... This will trick the browser
think you are trying to load a new file, therefore, solve the cache
problem.
It's there to make sure that you have the current version. If you change your website and leave the name as before, browser may not notice the change and use old CSS from its cache. If you add version, the browser will download the new stylesheet.
If you set caches to expire far in the future adding ?v=2 will let the server know this is a new file but you won't need to give it a unique name (saving you a global search and replace)
HTM5 boilerplate also includes it in their project.
Check this video also: HTML5 Boilerplate Walkthrough.
One of the reason could be to bypass file caching. Same name CSS files can be cached by the servers and may result in bad display if new version has has layout changes.
This is to optimise browser-caching. You can set the header for CSS files to never expire so the browser will always get it from its cache.
But if you do this, you'll get problems when changing the CSS file because some browsers might not notice the change. By adding/changing the version-parameter it's "another" request and so it won't be taken from the cache (but after the new version is cached, it's taken from there in the future to save bandwidth/number of requests until the version changes again).
A detailed explanation can be found at html5boilerplate.com.
My knowledge is pretty much out of date regarding websites, but the variable stored in the 'href' argument is received by the browser through HTTP. Using the usual tricks in URL-rewriting you could actually have an arbitrary script that produces CSS-output when called. That output can differ, depending on the argument.
I was browsing the html of my favorite site...ahem...and I saw this in the markup:
<link href="/Content/all.min.css?d=20090107" rel="stylesheet" type="text/css" />
what does "?d=20090107" do? I'm assuming it's a date of some kind, but I'm not sure why it's in the path to the file. Any ideas?
That is there to add some uniqueness to the filename, so that when they change the CSS file, they can change the extra bit to be totally sure that every client will reload the CSS rather than use a cached version.
The webserver will ignore the parameter and serve /Content/all.min.css normally
Note: While it's possible the CSS is dynamically generated, this is a common idiom for ensuring a reload, and given the parameter is a date, it seems quite likely.
Edit: Podcast 38 mentioned this...
We’ve been using the Expires or
Cache-Control Header since we
launched. This saves the browser
round-trips when getting infrequently
changing items, such as images,
javascript, or css. The downside is
that, when you do actually change
these files, you have to remember to
change the filenames. A part of our
build process now “tags” these files
with a version number so we no longer
have to remember to do this manually.
It's to "clear the cache" every time the style is updated. I would speculate that whoever is responsible for those styles increments it every time there is a change. It's because the browser sees a different URL in the style field, so it will grab the latest version, even though it's technically in the same place on the server.
As helpfully pointed out in the comments, css files often have their expiry set well into the future, this method is a nice sidestep to cache related headers.
Quite a useful trick.
It is to make the browser think it is a new file every-time to it refreshes its cache.
Very useful when your stylesheets change regularly...
This is SO's css path http://sstatic.net/so/all.css?v=6184" what is this ?v=6184"?
What it does? if it useful then how to use this? can i use this on any site PHP, ASp.net etc
It's a way to control caching. When the value of the "v" parameter changes, the browser will consider it a different URL and ask for a new copy of the file instead of using its cached copy. This technique is often used to "version" static files by providing something like a timestamp in the query string that marks when the file was last changed.
It's a query string. It can be parsed by server-side processes for allowing variable parts of the stylesheet, or it can be used to disable caching by browsers or proxies.
I found out that some websites use css tag like style.css?ver=1. What is this?
What is purpose of ?ver=1?
How do I do it in code?
To avoid caching of CSS.
If the website updates their CSS they update the ver to a higher number, therefore browser is forced to get a new file and not use cached previous version.
Otherwise a browser may get a new HTML code and old CSS and some elements of the website may look broken.
Adding '?ver=1' makes the HTTP request look like a GET query with parameters, and well-behaved browsers (and proxies) will refuse to cache parameterized queries. Of course well-behaved browsers (and proxies) should also pay attention to the 'Cache-control: no-cache', 'Expires', 'Last-Modified', and 'ETag' response headers (all of which were added to HTTP to specify correct caching behavior).
The '?ver=1' method is an expensive way to force behavior when the site developer doesn't know how (or is too lazy) to implement the correct response headers. In particular, it means that every page request is going to force requesting that CSS file, even though, in practice, CSS files change rarely, if at all.
My recommendation? Don't do it.
The purpose of the ?ver=1 is to parameterize the css file, so when they publish a new style.css file they up the version and it forces the client to download the new file, instead of pulling from the cached version.
If you are developing a web application in HTML and CSS or any other technology, and you are using some external CSS or JS files, you might notice one thing that in some cases if you made any changes to your existing .css or .js files then the browsers are not reflecting the changes immediately.
What happens in that case is that the browser do not download a fresh copy of the latest version of the .css and .js files, instead it uses those files stored in your local cache. As a result the changes you made recently are not visible to you.
<link rel="stylesheet" href="style.css?v=1.1">
The above case when you load the web page the browser will treat "style.css" as a different file along with "?v=1.1". Hence the browser is forced to download a fresh copy if the stylesheet or the script file.
I think that ?ver=1 is for the version no. of the web app. Every time a new build is created, the app can update the ver to the new version. This is so that the browser will load the new CSS file and not use the cached one (both use different file names).
You can refer to this site: http://www.knowlegezone.com/36/article/Technology/Software/JavaScript/CSS-Caching-Hack----javascript-as-well
IMO a better way to do this would be to include a hash generated off of the file size or a checksum based on the file contents or last-modified date. That way you don't have to update some version number and just let the number be driven off of the file's changing properties.
I have a legacy application that I needed to implement a configuration page for to change text colors, fonts, etc.
This applications output is also replicated with a PHP web application, where the fonts, colors, etc. are configured in a style sheet.
I've not worked with CSS previously.
Is there a programatic way to modify the CSS and save it without resorting to string parsing or regex?
The application is VB6, but I could write a .net tool that would do the css manipulation if that was the only way.
You don't need to edit the existing one. You could have a new one that overrides the other -- you include this one after the other in your HTML. That's what the "Cascading" means.
It looks like someone's already done a VB.NET CSS parser which is F/OSS, so you could probably adapt it to your needs if you're comfortable with the license.
http://vbcssparser.sourceforge.net/
One hack is to create a PHP script that all output is passed through, which then replaces certain parts of CSS with configurable alternatives. If you use .htaccess you can make all output go through the script.
the best way i can think of solving this problem is creating an application that will get some values ( through the URL query ) and generate the appropriate css output based on a css templates
Check this out, it uses ASP.NET and C#.
In my work with the IE control (shadocvw.dll), it has an interesting ability to let you easily manage the CSS of a page and show the effects of modified CSS on a page in realtime. I've never dealt with the details of such implementations myself, but I recommend that as a possible solution worth looking at. Seeing as pretty much everyone is on IE 6 or later nowadays, you can skip the explanations about handling those who only have IE 5,4,3 or 2 installed.
Maybe the problem's solution, which is most simple for the programmer and a user is to edit css via html form, maybe. I suppose, to create css-file, which would be "default" or "standart" for this application, and just to read it, for example, by perl script, edit in html and to write it down. Here is just the simple example.
In css-file we have string like:
border-color: #008a77;
we have to to read this string, split it up, and send to a file, which will write it down. Get something like this in Perl:
tr/ / /s;
($vari, $value) = split(/:/, _$);
# # While you read file, you can just at the time to put this into html form
echo($vari.":<input type = text name = ".$vari." value = ".$value.">");
And here it is, you've got just simple html-form-data, you just shoul overwrite your css-file with new data like this:
...
print $vari[i].": ".$value.";\n";
...
and voila - you've got programmatical way of changing css. Ofcourse, you have to make it more universal, and more close to your particular problem.
Depending on how technically oriented your CSS editors are going to be, you could do it very simply by loading the whole thing up into a TextEdit field to let them edit it - then write it back to the file.
Parsing and creating an interface for all the possibilities of CSS would be an astronomical pain. :-)