Standards
I've been doing a lot more web work lately, including javascript, so I have become a bit more sensitive regarding standards. Standards are good...adhering to them generally gives you predictable behavior and will give you (mostly) consistent appearance across browsers. Unfortunately, as I've been working more towards standards compliance, my contempt for Microsoft has grown. Take javascript, for example. In many cases, Microsoft has either implemented their own proprietary features, such as the case with the events model, or poorly supported the existing standards. There are also some oddities with XHTML support.
Anyway, enough bitching about MS. One of the things I've noticed along the way is that many sites run in "quirks" mode. For a comparison of standards-compliant vs. quirks mode you can go here. The easiest way to determine which mode a site is running in is to go to Tools -> Page Info in Firefox (you *are* using Firefox, right?). From there, you will see an entry called Render Mode that will tell you what mode the page is running under. I couldn't find a way to determine this in IE, and I don't have any other browsers currently installed to see where you can find this information when using them.
Fortunately, for ASP .NET developers, there is a lot of work going into Whidbey to make it easier to build standards-compliant sites. I stumbled across this article from a couple years ago on Scott Guthrie's blog.
Anyway, enough for now, back to work.