I don't want to sound offensive, but after only three weeks of doing CSS, you think your stuff is worth money? Maybe it is, but from what I've seen from beginners / intermediates, the code is an absolute mess and it's hard to take it seriously.
Also, what would make anyone purchase your menu instead of use on of the thousands that exist for free? CSS isn't really a money making script, it's use should be to make your sites more semantic and easy to alter. It's also not something that is hard to learn..
I'm sure you'd make some money from some people but I wouldn't get my hopes up at all.
You'd probably make more money if you threw it up for free and put adsense on the page. The menu looks nicer than a lot of them do, so that could be what is used to draw more people in.