Standard Web Banners

All measurements are in pixels. 

Size	Style	Gif Weight	Flash Weight
468 x 60	Full Banner	20 KB	30 KB
728 x 90	Leaderboard	25 KB	35 KB
336 x 280	Square	25 KB	35 KB
300 x 250	Square	25 KB	35 KB
250 x 250	Square	25 KB	35 KB
160 x 600	Skyscraper	20 KB	30 KB
120 x 600	Skyscraper	20 KB	30 KB
120 x 240	Small Skyscraper	20 KB	30 KB
240 x 400	Fat Skyscraper	25 KB	35 KB
234 x 60	Half Banner	15 KB	20 KB
180 x 150	Rectangle	15 KB	20 KB
125 x 125	Square Button	15 KB	20 KB
120 x 90	Button	10 KB	20 KB
120 x 60	Button	10 KB	20 KB
88 x 31	Button	10 KB	10 KB

Common, But Not Standard Banner Sizes

Size	Style	Gif Weight	Flash Weight
120 x 30	Button	10 KB	10 KB
230 x 33	Small Banner	15 KB	15 KB
728 x 210	Large Leaderboard	30 KB	40 KB
720 x 300	Large Leaderboard	25 KB	35 KB
500 x 350	Pop-up	30 KB	40 KB
550 x 480	Pop-up	30 KB	40 KB
300 x 600	Half Page Banner	35 KB	45 KB
94 x 15	Blog Button	10 KB	10 KB