There are many things that all webmasters must do on a regular basis to ensure that their web sites remain useful and functional. Some of tasks you should be performing are listed below.
You must promote your web site constantly. Every single day you should do something, anything, which attempts to get people to your site. This is extraordinarily critical in order to ensure that people continue to visit your site day after day. The "Advertising" section describes many of techniques that you can use to get your site noticed.
Advertising - http://www.internet-tips.net/Advertising/Advertising.htm
Check your links
Another task that must be performed on a regular basis is checking for "link rot". This is tendency for broken links to appear all over a site. It is most common with external links (sites move, are abandoned or are modified all of time) but can occur occasionally with internal links.
Link Rot - http://www.internet-tips.net/Webmaster/maintlinkrot.htm
Change Your Site
People expect sites on web to be constantly changing. If your site is static and unchanging there is no reason for someone to come back again - after all, they've already seen it so why return? One major way to get them to come back is to change content constantly and to be sure that your visitors know it is changing.
Monitor Your Site
Subscribe to a service which checks your site on a regular basis. This is important, as if your site is constantly "bouncing" you will find it being removed from search engines and your visitor levels will drop.
Review Your Statistics
A task you should be performing on a regular basis is to review your statistics. At a minimum, you should check your page counts to be sure that your site is being viewed. At best, you need to know where people are coming from, which browsers they are using and what they visited while they were at your site. A webmaster who does not have access to statistics is a crippled webmaster who has no idea how effectively his website is performing.