CSS CSS
There is a very little known method of injecting javascript int CSS files. It would not work in all the browsers (works in my latest IE8) but it is important fact to know.
Internet Explorer is often causing issues as there is no effective way of debugging the websites css and javascript. Firebug is one of the best tools i have ever seen as php developer. Now using a simple link you can run it in IE as well!
The most amazing thing Microsoft has done in years was releasing virtual pc and testing system images for free! Now you can install many operating system on your virtual pc and test the website in all possible browsers!

I read this book a while ago so i cant remember exactly every detail abou it but i remember it was a decent book.
The only problem i had with it that i could not believe that there are no better ways to create all these layouts than incompatibility hack and layouts through margins/paddings etc :- ))
So basically i could not believe that CSS implementations are so CRAP! Even that the CSS as technology has a very good ideas and it makes perfect sense.