Tool
Upload your creative and see how it looks in real ad placements. Check before you launch.
A creative that looks great in Photoshop might fall flat in context. Text too small for mobile, colors that clash with the page background, key visuals getting cropped — all problems you can catch with a quick preview before spending your ad budget.
Mobile banners (320×50) have almost no space — stick to your brand name and one short line. Interstitials (320×480) give you room for a story, but make sure the close button doesn't cover important content. Desktop sidebars (160×600, 300×250) sit next to articles, so your ad needs enough visual contrast to stand out without being obnoxious.