"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."

Correct use of stopping event propagation and bubbling; talks about jQuery but is equally applicable to other frameworks like YUI.

Faaaaast == good

Compatibility tables for features in HTML5, CSS3, SVG and other upcoming web technologies

Specifically the image with the text "The User's Display Screen" in it. Note the suckiness of information exposed by Internet Explorer, making it impossible to correctly center windows opened via JavaScript.

I've written a test page to investigate this behaviour in the past. This is more complete, and shared with the world to see! Kudos!

(sigh)

"Another thing to consider is how “layout” affects scripting. The clientWidth/clientHeight properties always return zero for elements without “layout.” This can be confusing to new scripters and is different to how Mozilla browsers behave."

Ugh.

JavaScript style property names and browser supprt

Includes a nice brief history of AJAX in the "Round pegs, square holes" section

I now use Chrome, so dated.