need help add drop down menu to asp.net header control

[aboutjav.com]

Hi,

I am new at asp.net and want to add a horizontal dropdown menu like
toolstripmenu in windows form. I found a drop down menu written in
javascript (DHTML). How do I add to my asp.net project. I have a
masterpage which contains the navigation panel, header, and the main
content panels. I prefer to add to my header panel, where I originally
drag a header control, which contains a table with just plain links
for HOME, CATEGORIES, etc..

I want to replace the links with this nice looking drop down menu bar.
When I open the header.cs.aspx file, I don't know where to add the
scripts.

Please advise...

thanks.