I need some help and i need it explained well because i am rubbish at working out coding

Basically what i want to do is create a menu horizontal across the page that when the user clicks on a button a drop down menu appears which is kind of transparent over the images below.

Can any help be offered?

Please correct me if this is the wrong section.

Here's a good start
http://www.dynamicdrive.com/style/cs...y/category/C1/