Need help with CSS on WP blog part of site

I have completed my web business site but noticed that the WP portion is all screwed up on the categories and single post pages. I have uploaded my CSS pages to the site and for the style.css I make reference to the 3 style pages that are used. I normally troubleshoot in Chrome using web developer tools but these have me baffled. I know that I will have to add styles for the categories and the single post page items but I am not sure where to begin. You can see the mess at http://foxdenwebsolutions.com/blog. I really struggle when it comes to WP but I have to become comfortable with it as many clients seem to be wanting to go in that direction so they can maintain the site themselves instead of paying the web design/developer to maintain it. Any help or suggestions would be greatly appreciated. Thanks.

Looking at this more in depth, it seems to be a problem between the sidebar and the actual 10 column and 6 column setup. If I remove the sidebar, I get an error. So I am wondering if I need to remove the 6 column since that would be where the sidebar info would be. Any thoughts from anyone on this?

This sounds like an issue of “how to use Wordpress” rather than a CSS question. I recommend moving this thread to the Wordpress forum.