2. First Aid Git
“A searchable collection of the most frequently asked Git questions.” This looks useful for anyone with average or below average skills with Git. Currently has 38 separate topics that can be found via an on-page search filter.
3. Periodic Table of ARIA 1.0 Roles & Attributes
This is two separate pages — which I suppose brings this list to 21 — documenting detailed info on ARIA roles and attributes.
Just click on a role or attribute and an overlay will display information from the spec on that feature.
4. Is Service Worker Ready?
The Service Workers specification is a promising (no pun intended!) new standard that isn’t quite ready for production because of lack of browser support and being still in flux. This little info site has a description of the spec’s features and how they measure up in the different browsers.
5. Browser support for broken/missing images
This is something we probably all take for granted most of the time. This is a CodePen-based document by Bart Veneman that outlines exactly how the different browsers/OSes handle broken images (with placeholder, alt text, border, etc.)
6. 2014 Responsive Report
This is an annual responsive survey conducted by the folks at Gridset. Over 1000 participants in this survey provide information on challenges they face in their RWD workflow, in relation to clients, testing, and so forth. The survey also looks at optimism (or lack of it), trends, and tools used in RWD.
7. Typography Cheatsheet
“A comprehensive guide to using proper typographic characters, including correct grammatical usage.” Also available as a one-page PDF, this includes the keyboard shortcuts to produce the different characters for both Mac and Windows, which can be handy.
8. ARIA Examples
Accessibility expert Heydon Pickering’s excellent compilation of HTML examples demonstrating different use cases for various ARIA features. Demos and code for 9 different examples. A really nice starting point for anyone looking to get into advanced ARIA implementation.
9. ES5 Mobile Compatibility Table
10. iOS Fonts
“Every font. Every iOS version.” Speaking of being really specific and mobile, this is an insta-filterable list of which fonts are available on iOS devices, including the Apple Watch.
11. CSS Filters Playground
A simple interface to mess around with the various parts of the filters spec. Useful also because you can choose a custom URL and even try it out with an iframe or video.
12. Git Cheatsheet
An interactive, clickable cheatsheet for Git commands. The different sections have deep linking too, which is a nice bonus for sharing.
14. Regular Expressions 101
A very nicely done little app to help you test and learn regular expressions. I like how it displays an “explanation” and “match information” and it lets you choose 3 different flavors of regex.
This is a mobile app that “provides compatibility tables for features in HTML5, CSS3, JS API, SVG and other upcoming web technologies.” I’m assuming the name is supposed to be a play on “Can I Use Mobile”, but they don’t seem to use that exact phrase, probably to avoid copyright issues, but I’m not sure.
16. DevTools Snippets
“A collection of helpful snippets to use inside of browser devtools.” Looks to be about 20 of them and you can contribute your own.
17. Codrops CSS Reference
In case you missed this one, Codrops, with help from Sara Soueidan produced their own very nicely designed and comprehensive CSS reference.
18. Screen Sizes
A really extensive list of mobile devices and laptops with their respective screen sizes. The devices even link to their product pages on Amazon.
19. Frontend Guidelines
20. CSS Ruler
A simple, interactive little tool to help you understand the different ways CSS handles relative and absolute font sizes.
英文链接：20 Docs and Guides for Front-End Developers