Sure, content, functionality, timeliness and value are crucial, but without traffic, and lots of it, few Web sites can be considered successful. But getting it takes work. You can get traffic from links on portal sites, advertising links within a vertical industry segment, and listings in directory and search engines. Portal links can be effective traffic generators but can also be somewhat expensive and not always selective.
Advertising is equally expensive and sometimes reaches too narrow an audience.
Thus, most Web sites hope for a decent listing in the pleth ora of search engines that litter the Web landscape. But being listed is somewhat of a field of dreams in itself. It helps to understand how search engines work. For example, the folks at Google, one of the largest search engines, pointed out to me recently that true search engines differ from directory servers, which can be populated by humans who review Web sites for content. True search engines use sophisticated algorithms to rank and index Web pages.