We've all seen language documentation at one point or another. Occasionally you will find yourself in a spot where you need to look up something, and have no internet access or nothing saved offline.
Obviously the first place to look at is the source code if all fails, or other tools like xcode have built-in documentation but it is not always the case for all languages/tools.
Here's where Zeal comes into play, it was inspired by Dash. It is an awesome application where you can download docsets for easy offline usage for whatever languages you use. I'll be honest about it, I didn't know such of tool existed for so long. I hope you find it to be useful in your quest.
Note: Zeal version is free for linux, and windows. Dash is for mac, dash is free to use but will nag you to purchase, and if you have the dough please support them. (Not sponsored by Dash :) )
Let me know of other tools alike, or other ways you browse language documentation.