With estimates of over 200 different ad sizes and shapes being identified on sites that accept banner ads, the lack of standard sizes is a troubling issue which has caused advertisers and their agencies to spend time and money resizing ads to fit individual sites. Some less sophisticated sites have gone so far as to take off-size banners from advertisers and reduce them to fit -- a technique that often yields less than desirable results.

These are voluntary guidelines and not "standards," the organizations emphasize. Nevertheless, Web publishers who want the cooperation and goodwill of the advertising community are well advised to adopt these guidelines -- which means redesign work is in order for a number of Web sites.