DevDocs is a Chrome app which enables offline documentation browsing for many web and other development technologies.
All the available documentations are listed in a left-hand sidebar. Click "Select documentation" bottom-left, check the boxes next to anything you need, click Save and the new technologies are collected together at the top of the sidebar.
You can browse them much like any other web-based manual. Expand something like HTTP, select an interesting section such as Response Status Codes and click a code to find out what it means. Or just use the fuzzy search feature to find all potential matches.
DevDocs is easy to use and brings most of the documentation you need into one place. There are some omissions, though - no Java? - and with no updates since May 2016 these gaps may not be filled any time soon.