Sitemeter bug takes down thousands of web sites (for Internet Explorer users)
It's likely that the bug is due to tracking code changes Sitemeter has been rolling out. Visitors to web sites using the code who are using IE will see the page start to load, and then get an error message. When you click OK to make the error message go away, the entire site goes with it. Nice.
Thanks Darren Paul!
Update: It looks like the bug has been fixed.