The navigation isn't centered.

Things to improve:
1.The green bar on the top, the gradient is not very effective, and its to flat.
2.You have been heaping text that says "imagespotadvertising" which takes away alot of appeal from your Logo, kind of taking the branding away from the logo.
3.Your navigation isnt centered.
4.The blue box that your navigation is in, i dont know if it should be 100% or just the width of layout.
5.The stroke around the advertisment, not effective, a 1px black border would look better.
6.Your logo, ummm its nothing? What is it supposed to be? Some randomly made boxes with a line above them.
7.You are using WAYY to many gradients.
8.Your content area is bland, do something with it, maybe make a nice background for it (maybe a very simple but effective pattern)
9.Different color selection, its been used, and used, and used, and used.
10.Needs more professional appeal, it will attract more users.