There are many sizes and standards of ad banners within the Google Network. Some do outperform others. Google likes to have the flexibility of having as much inventory of each ad banner size so they can maximize what they can display on any given page. As a general rule, wider ad sizes tend to outperform taller ad sizes. This is because wider ads a more reader-friendly. Wider ad sizes let readers read more text at a glance, avoiding having to skip a line and return to the left margin every few words. This makes sense, right?
If you have a finite ad banner budget, you might want to keep to these 5 banner sizes.
1. The 336 x 280 Large Rectangle
2. The 300 x 250 Medium Rectangle
3. The 728 x 90 Leaderboard
4. The 300 x 600 Half Page
5. The 320 x 100 Large Mobile Banner