applying theme to a pop up page that does not contain Header

Hi All,

I Have developed themes for our portal.
I am able to apply the CSS file to all the Pages.
The way i have done is; i have a Header Usercontrol.
In this user control i have defined the CSS file i am using, like CSS file for Purple color.
then i am registering the header in all the pages and use the header there.
The problem is implementing themes for pop up pages. Since i am not using header there the theme is not applying.
Can someone suggest me some ideas on this.

Thanks & Regards,

Arun:confused:

How are you creating your popups? Why not make a separate file that includes what you need?

The Pop Up is also a web page.
I will give a scenario: there is something like add user, when i click on it, the pop up page appears as a small window with sharepoint people picker control and two buttons.