Need help with JavaScript!

[Yedidya]

I have a website called Dan's Roms, in Hebrew.
I have a JavaScript errors on: hxxp:dan.mihopa.com/roms/new/ [nonactive] in the menu, go down, and the first bold item, click on it, then you'll see the errors.

Also, I'd like to put 3 more things: On the pop-up download window (which you'll see if you'll fix the JavaScript bugs), I want to include a random banner.

I want to put an image that will contain a combination of letters and numbers, and then the user will have to write them in an input, and then click on the button, and then start downloading.

And last, I want to include a tree menu script on the right, called dTree.

Please assist! Contact me @ ICQ no. 94341632, or here. Thanks!!!