www.yahoo.com suffered an outage for a short period this morning.
Yahoo!'s main website is currently the 14th most visited website in the Netcraft Toolbar dataset, so even a relatively short outage like this will have affected a large number of people. The site also suffered a worldwide outage last month.
Many of Yahoo!'s websites, including www.yahoo.com, are served with the YTS/1.18.5 (Yahoo! Traffic Server) header. Traffic Server was originally developed by Inktomi Corporation as a proxy cache for web traffic and streaming media. The company was later acquired by Yahoo! in 2002.
Yahoo!'s widespread use of YTS was largely hidden until November 2008, when the YTS/1.17.8 server banner was seen on more than 220,000 Yahoo!-hosted sites. Prior to that time, the sites did not return a Server header at all.
Netcraft's November 2010 Web Server Survey includes nearly 1.4 million sites using YTS.