It looks like the white section is inside of a larger section with the grey background, and the color on the sides is actually just part of that larger section. The background of the div with id "section5" has a background of #F5F5F5 (this is the larger, grey section). Meanwhile the smaller white section inside of it is a div with the id "section2" and has a background of #FFFFFF. That section's margin property creates additional space around it, where you're seeing the grey. If you set the margin property to 0 and set the width so it fills the entire page, that should fix it.