Pop-up polls on Web sites are now as common as subscription cards tucked between the pages of your favorite magazine. And for good reason. Marketers have discovered that online surveys generate a mother load of valuable information about site usability, visitor opinions and attitudes, new product ideas and improvements, and much more. Online surveys and polls are easy-to-implement,low-cost marketing research tools. They're a snap to include on your site -- either through a Web server's CGI sc.