The choice of which software powers your Web site or intranet can make as big a difference as whether you choose to play tennis on grass or clay. But choosing Web server software involves weighing many more advantages and disadvantages than the choice of court surface, and the stakes for your business are probably a lot higher. This software is the communication engine behind all Web sites, and it's increasingly called on to do more than simply deliver Web pages and images to browsers. Web server software ties in intimately with your Web applications and can even dictate the technologies those applications employ. The Web server software also plays a vital role in determining how many browsers your site can service simultaneously and how quickly.