Here are some ideas that might help. Forgive me if someone else mentioned them already:
1) I find the pop-up menu items a bit difficult to read due to the light blue box, maybe an even lighter blue or white background will make them stand out more
2) As mentioned, the drop down menus cover the body text (a usability issue). It might be better if you design the drop down navigation to drop down only one line and view the sections across and to the right .
3) Copyright notice should also include All Rights Reserved
4) On the pages with above the fold content, there isn't really a need for "Back to Top". If you do decide to leave this in, all of the back to top links are not working. You could separate the body copy by creating separate pages (e.g., clients and testimonials have separate pages).
I hope some of this helps.