What is your favorite source of information on various browsers?

As you might have noticed, we are now shipping intellisense/validation schemas for XHTML and HTML 4.0. It is easy to obtain information for standard schemas from the W3C Web site. However, with specific browsers it is more difficult. What is your favorite source of browser information? Blooberry? O'Reilly books? MSDN? Netscape DevCenter? Netscape seems to have pulled information on Navigator 4 from their website though...

Or do you think it is sufficient to simply target XHTML Strict? Did you see many incompatibilities between modern browsers in the XHTML support? How do you figure out what works in IE6, NN7, Opera and Safari? How's about CSS support? Is CSS1, CSS2, CSS2.1 and CSS-IE6 enough or should we add more browser-specific schemas? How's about JavaScript? Should we target W3C DOM (DOM1? DOM2? DOM3?). Currently we provide linked triplets such as XHTML Transitional (markup) + CSS2.1 (inline styles) + W3C DOM1 (javascript). Shall we provide a way to choose each of them separately? If no, which is a good set of combinations?

We would like to make our schemas better so pointers to reliable sources of information as well as general feedback are very appreciated.