⇨ How Browsers Work

As a web developer, learning the internals of browser operations helps you make better decisions and know the justifications behind development best practices. While this is a rather lengthy document, we recommend you spend some time digging in; we guarantee you'll be glad you did.

All you have ever wanted to know about the internals of Web browsers and more...

I link to the document on HTML5 rocks which is nicely presented but the original is available on Tali Garsiel web site.

(via FunctionSource)