Hi, friends!

Can anyone please tell me what programming language is Craigslist written in? Whenever I click on an ad on Craigslist, its url ends with .html. How is that possible? If you create an add on Craigslist, you're basically adding information to a database (i.e. MySQL) and when someone views your ad, it's basically fetching from database. I think Craigslist is written in PHP, but why all the ads have a .html url?

Really confused....