Title and child pages

Hi there, my site title has become bold, I think since updating the theme to the latest version. I don't want it to be bold, is there CSS code to change that please? Also, I have child pages under a parent page. When clicking on the parent it highlights all of the child pages, I only want it to highlight when it's on hover. I also need to change the size of the font in the drop down child pages please. Thanks!