Additionally, any other web sites that grow in size or traffic levels will greatly benefit from a professional Web host provider. Please note that certain free providers allow you to pay to gain additional space, bandwidth, and features, blurring the line between free and Professional Web host providers. Professional Web hosting services tend to have increased customer support, and also have far more features and ancillary services. A professional Web hosting service also allows a web site to have additional storage space, up to and including using an entire server or even multiple servers dedicated to one Web site. Professional Web hosting services also tend to have faster, redundant backbone connections to the Internet - increasing site uptime and decreasing site download times.
Customer service is probably the most important of all.
This is where the human element is so important. The better the quality of people at your Web host provider, the faster and more often your Web site will be up. Reliability is also very important. Proper Web hosting is actually very complex - Web servers must be maintained, the facilities housing the servers must be capable, and connectivity to the Internet should be fast enough and redundant, if possible. If any of these fails, then your Web site is down - period.