Single huge .css file vs. multiple smaller specific .css files?
This is a hard one to answer. Both options have their pros and cons in my opinion.
I personally don't love reading through a single HUGE CSS file, and maintaining it is very difficult. On the other hand, splitting it out causes extra http requests which could potentially slow things down.
My opinion would be one of two things.
1) If you know that your CSS will NEVER change once you've built it, I'd build multiple CSS files in the development stage (for readability), and then manually combine them before going live (to reduce http requests)
2) If you know that you're going to change your CSS once in a while, and need to keep it readable, I would build separate files and use code (providing you're using some sort of programming language) to combine them at runtime build time (runtime minification/combination is a resource pig).
With either option I would highly recommend caching on the client side in order to further reduce http requests.
EDIT:I found this blog that shows how to combine CSS at runtime using nothing but code. Worth taking a look at (though I haven't tested it myself yet).
EDIT 2:
I've settled on using separate files in my design time, and a build process to minify and combine. This way I can have separate (manageable) css while I develop and a proper monolithic minified file at runtime. And I still have my static files and less system overhead because I'm not doing compression/minification at runtime.
note: for you shoppers out there, I highly suggest using bundler as part of your build process. Whether you're building from within your IDE, or from a build script, bundler can be executed on Windows via the included exe or can be run on any machine that is already running node.js.
A CSS compiler like Sass or LESS is a great way to go. That way you'll be able to deliver a single, minimised CSS file for the site (which will be far smaller and faster than a normal single CSS source file), while maintaining the nicest development environment, with everything neatly split into components.
Sass and LESS have the added advantage of variables, nesting and other ways to make CSS easier to write and maintain. Highly, highly recommended. I personally use Sass (SCSS syntax) now, but used LESS previously. Both are great, with similar benefits. Once you've written CSS with a compiler, it's unlikely you'd want to do without one.
http://lesscss.org
http://sass-lang.com
If you don't want to mess around with Ruby, this LESS compiler for Mac is great:
http://incident57.com/less/
Or you could use CodeKit (by the same guys):
http://incident57.com/codekit/
WinLess is a Windows GUI for comipiling LESS
http://winless.org/
Historically, one of the main advantages x in having a single CSS file is the speed benefit when using HTTP1.1.
However, as of March 2018 over 80% of browsers now support HTTP2 which allows the browser to download multiple resources simultaneously as well as being able to push resources pre-emptively. Having a single CSS file for all pages means a larger than necessary file size. With proper design, I don't see any advantage in doing this other than its easier to code.
The ideal design for HTTP2 for best performance would be:
- Have a core CSS file which contains common styles used across all pages.
- Have page specific CSS in a separate file
- Use HTTP2 push CSS to minimise wait time (a cookie can be used to prevent repeated pushes)
- Optionally separate above the fold CSS and push this first and load the remaining CSS later (useful for low-bandwidth mobile devices)
- You could also load remaining CSS for the site or specific pages after the page has loaded if you want to speed up future page loads.
I prefer multiple CSS files during development. Management and debugging is much easier that way. However, I suggest that come deployment time you instead use a CSS minify tool like YUI Compressor which will merge your CSS files into one monolithic file.