if condition depending on url or address

[Super Jinni]

OK, let me say it in this way,

I have some customized header, so I want to change depending on the page that user going to visit, so some pictures will change in the main header, and some colors will change too.

so, I want to do that according to the url of the page that user visit. or according to the last part of the the url like what in red in the first post in this thread.

so, I want to do it in this way,

<if condition (the url is:www.whatever)> show this header</if>

or

<if condition (the last part of the url is: (/?do=buddylist or whatever)>show this or do this</if>

so I want to set a condition for whatever according to and depending on url or part of it.

I hope I could explain it clear enough. and sorry for my poor English.

so, is there any way to do something like that?

thanks again