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.