ASP / CSS header and footer

Hi, many thanks for your time.

I am a novice at ASP so any help would really be appreciated.

The pages I create currently include a header and footer with ASP

However the issue I am having is how can I select through CSS what tab needs to be highlighted depending on what page the user is in as the CSS is linked through the header.

I originally started thinking that the ACTIVE selection on the LI list needs to be replaced with a variable, and when that variable is called depending on the page, then that would indicate what menu option should be highlighted.

Unfortunately I am unsure on how to tackle this, any information would be really appreciated.

Kind regards,

Gabi.