Hi there, when you say “header page” are you talking about the main page of your site, your “home” page?
If so, you can specifically target the main home page by preceding the selectors with .home, such as below:
.home .entry-content, .entry-summary {
padding-top: 100px;
}
If you are not using it, you might want to start using the web inspector in Firefox (I see you are using it). It is an invaluable tool when doing CSS. We have some brief screencasts on How to Find Your Theme’s CSS which will get you started.
There is also more information on the Firefox web inspector at the Mozilla website.