I'm posting this thread because I'm not exactly an expert with .css, .html, .php, javascript, etc., and usually make the dumbest mistakes possible.
I'm currently trying to match my vBulletin Forum skin with a heavily modified version of my Joomla skin. For this I required a javascript date function at the very top of my header for continuity sake and while it works alright for the most part, I've noticed a rather embarrassing issue.
The date on my header as of this posting is Monday November 2
th, 2009, rofl

I just hope nobody reads the date out loud when visiting my site or they'll cover their monitor in spittle.
...guess I'm gonna have to address the issue.
Just out of curiosity, what are some of your more embarrassing, public, coding mistakes?