Comps is an extension inspired by the PixelPerfect Firefox extension. It allows you to load images from your local computer and easily overlay them onto your website for comparing your code against a given design.
To get started, click the Comps button, then drag a comp to load to the drop zone in the bottom left hand corner of the page. Click a comp's thumbnail to load it.
You may click-and-drag a comp to move it around, or use the provided arrow buttons to nudge it 1px at a time to get that perfect line-up. Mousewheel on a comp to change its opacity. Ctrl-click a comp's thumbnail to remove it.