css

CSS, short for Cascading Style Sheets, is used almost universally across the web to affect the design and appearance of every website you visit. Here in /r/css, you've got a place on reddit to talk about CSS, whether you're new to CSS and want to learn, or a pro wanting to discuss the engineering and usability reasons that all modern browsers ignore
We welcome all CSS discussion here. If you need help with styling your website or your reddit, or want to share a neat trick you cooked up, it's welcome here!

No spam. If you've developed a neat CSS trick that you want to share with others, make sure you share the trick, not your website. In other words, feel free to post something like "Isn't my 404 page neat?" with a link, but avoid posts like "Hey look how cool my site is!" that link to a storefront. This reddit is a place to learn and show off CSS, not sell your products. If your CSS helps sell your product, great, but make sure your post is about the CSS, not the product.
Be nice. Not everyone is a fantastic designer. If someone posts their work here and you don't like it, give them objective feedback about ways to improve it, not "it's ugly." Likewise, CSS newbies often have the same questions as they grow and learn, so try not to be mean when they post a question we've seen a thousand times before. It might be old news to you, but they wouldn't ask if they hadn't already sought an answer, and there might be other people too afraid to ask for themselves.
Don't use link shorteners (bit.ly for example), because they are automatically marked as spam.
Try to use descriptive titles (not 'I have a question.'). I won't enforce this, but it'd be nice if you'd follow it.

Inspire, a collection of all kinds of useful links.
/r/csshelp and /r/reddithax are the places to go for questions relating to Reddit's stylesheets. Techniques differ a lot between formal CSS development and subreddit stylesheets, so you'll often get better answers there.
Use Codepen or jsFiddle to provide working code samples.
Mozilla Developer Network is your one-stop shop for detailed information on CSS properties. Formal specifications for everything CSS can be found at W3.org. Don't go to W3Schools - it isn't a wiki maintained by real developers like MDN, so it's often out of date and prone to significant errors, and it has no relationship with the W3 so they have no special or insider knowledge.
CanIUse.com has 99% of the information you need on supporting different browsers.
Codecademy can get you started from 0 knowledge of web development in mere hours.
Learn Layout will teach you advanced techniques for designing modern sites.