Applying custom CSS styles to a particular DIV

Hello.

I am having problems getting SharePoint to honor my CSS on a particular page layout. I have linked to a custom CSS file in the masterpage (copy of Seattle). It is published and SharePoint sees the CSS link registration in the full source. However, I cannot style a group of web parts by editing my CSS file. For some reason, when I use F12 it seems corev15.css is still winning in the specificity battle.

I'm getting annoyed now, having spent the last 3 days off and on fighting this. I've linked to my aspx and css as a possible starting point.

I'm essentially looking to inherit styles from a particular DIV ID (#thefifthfamily) tostyle the web part header titles and its content to plain white text (since the background color clashes with the dark text). For something so simple in normal web development, this is an exercise in futility for me. Any help is greatly appreciated.  Thank you!