If you're ever bored and you're looking for something to distract you, try this for a change: go to your favorite blog, look for the "Valid XHTML" button and click it. Chances are, you will receive a lot of error messages. I tried this with the 20 blogs I visit the most and of those only two actually passed the validation. Now I don't mind the fact that a lot of blogs have invalid markup, I just think it's a little silly to put up a "Valid XHTML" button when in reality it's not valid at all. Now I know that a lot of blog templates have those buttons built into them and usually those templates are indeed valid XHTML, but if for whatever reason you managed to break the validity, remove the buttons. Actually, I think no one should have those buttons on their blogs even if their markup is indeed valid, because valid markup is nothing to be proud of. It's as if a C++ programmer said "look at me, my program compiles".
Don't get me wrong, I'm all for web standards, but it's not like its something so special, you should promote it on your website.

However, even worse than broken "Valid XHTML" buttons are "too cool for IE" buttons. Not only is it very arrogant to tell people which browser to use (or not to use), if your page is not working in IE 6, you're practically alienating > 70% of the people on the web. I'm not very fond of IE 6's CSS implementation myself, but to claim that a page is "too cool for IE" is just bogus. If your template doesn't work in IE 6, it's not because IE 6 sucks, it's because you've been too lazy to make it work. So far, I haven't encountered a single design that couldn't be made to work in all browsers including IE 6 without resorting to using tables. And in those rare cases where things just won't work, you can always use IE's conditional comments.