Not setting business goal
Problem sites usually start with problem people, especially those who act before thinking. If you are not sure what your site is supposed to accomplish, it will end up as confused as you are. Start with clear business goals for the site, identify very specific target markets, and set quantifiable objectives so you can mesure your success and enjoy your accomplishment.
Not Planning
No one knows your business and markets as well as you do. Think ahead about everything. If you have problems offline, fix them before you go online.
Underestimating the time and money it will take
Whatever uou plan, your site will take twice as long and cost twice as much as you estimate.
Not building a search-engine friendly web site
Thinking about "Me" rather than "You"
From navigation to content, too many site owners tell their own stories rather than what site visitors want to know. A little imagination goes a long way. Put yourself into the customers' shoes. What do they want to know and how easily can they find it?
What's in it for me? This is the question customers always ask and every site must answer from the first headline on the home page to the thank you message at the end.
Not updating your site
Waiting for traffic to click in the door
Search engines and an inbound link compaigh are the two most essential components of Web marketing, yet many people don't do even that.
Ignoring statistics
many site owners don't know they have statistics, let alone use them. They can's answer the simplest question about real trends in traffic.
Avoiding problems with the back office
Being Unwilling to change
Change is the only constant in the world.