Developing easy to use websites
In the end your business and websites are just tools to your customer. Tools exist to make work easier. Your customers want to do something, you are there to make doing it easier for them. If you have a buggy or hard to use site you arent making doing your job and they'll find someone else.
Usability is key to customer retention. Once they have found you through your extensive marketing and you have lured them in with your impressive design they have to be comfortable using your site or they will be unhappy with your service.
The key to making your sites more user friendly is to use the latest AJAX and to help the user along instead of trying to impress them with flashy effects. Give hints and correct data entry errors before they occur. Dont unnecessarily ask for confirmation for every action.
Also how the information is presented can be very helpful in making the site more usable. If you put too much text on a single page the user may be discouraged and not read it. If you put too little they will find it to be not very helpful or informative.