it looks to me like you're trying to superimpose the bottom div on top of the first div using the negative margin - which is giving you the gap.
It also looks like the only difference is that the bottom div is adding an image. If this is the case why not combine the two:
If this doesn't work because of your image or whatever, then I'd put that bottom div within the first div and use absolute positioning.
<div style="position:relative; z-index:1; margin: 0 auto 0 auto; padding: 0 0 0 0; width: 1000px; height: 800px; background::#ffffff url(image/frame.png) no-repeat top left; text-align: left;">