HTML & CSS Help Needed

I have a web page located at the link below. LINK- [login to view URL] I am wanting to add an additional header or button for an "About" page. The graphic for the button has been created and I have attempted to edit the CSS and HTML to incorporate the new "About" content but I cannot get the other navigation headers or buttons to align correctly. I have also included a link to the page that I created which IS NOT working correctly. LINK- [login to view URL] I am guessing that it has to do with the CSS and the width of the DIV with the class "content visible". This width is also referenced in the JavaScript file entitled "[login to view URL]". Can someone help me to fix the CSS so that all of the headers or buttons are aligned correctly? Thank you! Todd