Dude you need new fonts. Your creating a technology themed look and feel and forcing hand scripted fonts in for you main nav and header. That's a total conflict between the geometric shapes and angles within the background and the looser more organic shapes and curves of the text.
Use something that fits that style a lot better like Mini 7 or a personal favorite of mine House Gothic Light #4 which looks great, but has wide kearning so you can't fit as many items on a horizontal menu bar. Also if you're going to put white text on such a light grey background as your main nav you need to put either a dark dropshadow or duplicate the text layer in black and use the gauissan blur filter to make the edges of the text pop.
Uclap5 is right, framing each area with a simple 1 pixel edge would do a lot to house the content within the space of the browser window. Right now your left and right sides on the top banner look like they're missing something.
Also when moving from section to section there should be some veriaty within the header graphic. If you don't want to take the time to create different ones for each section then just change the color. Pretty simple to do in Photoshop using the Hue/Saturation adjustment under the Image menu. Save it out as a seperate file and drop that one into the correct scene in the flash file. (I'm assuming you built each "page" of the site as a seperate scene in Flash and have the main nav links directed to the appropriate scene). The in your content area have the section text headers be in the same/similar color to the graphical header, thus solidifing the relationship between the content and the overall section look and feel. Duplicating this color in the "hot" states of your main nav will also help ease the intuitiveness of the navigation and user experience.
Umm... Don't mean to sound discouraging or anything, all in all I like it, but really it's too empty/incomplete to provide really contsructive critisim.