1. Designing a website for a specific browser or resolution.

In many cases designers will create a website that is best viewed in Internet Explorer or only on a 1024x786 resolution monitor. However, a website should be designed to look the way it is supposed to in as many browsers as possible, and at the smallest resolution you are likely to come across.

2. Designing a site without the purpose in mind.

Some websites do not make the purpose of the site very clear. The user should be able to determine the purpose of the website from the home page. They shouldn't have to find the purpose by exploring the sub pages, because they probably won't.

3. Making the purchasing process difficult.

If your site is intended to sell products, the process of doing so should not be a difficult task for the user. When the user has an impulse to buy, they should be able to start the purchasing process instantly.

4. Hard to use navigation

If a user can not find the information they need or product they are looking for, they are likely to leave your site. With that being said, everything should be easy to get to from any page on the site. The user should also be able to determine what page they are on at all times, as well as how to get back where they were before.

5. Forgetting purpose of text

Text is meant to be read; it should contrast with the background, and have a readable font. Text should also be limited in graphics. Using html text not only lowers the page load time, but it allows users to enlarge the text, copy and paste the text, and allows search engines to read the text. Using text for design is fine when the text isn't an essential part of the information at hand.

6. Putting too much content on one page

Many websites try to pack a webpage down with content they feel is important and do not want the user to miss. However, the more content that is on a page the higher the chances are that the user will not see something. If you have too many items competing for attention, the user will focus in on only a few of them. Let the user decide what is important to them, and navigate to it accordingly.

7. Misusing Flash

Although Flash can be a very powerful tool in web development, it can also have a negative effect on a website. Many sites use Flash intros which are often annoying and impact the search engine optimization. If a Flash intro is necessary, an html link which doesn't require Flash should present and visible as soon as the page loads. However, using a "Skip" button often says that the information isn't important, in which case we probably shouldn't force the user to experience it as soon as they enter the website.

8. Over using graphics

Although graphics can make your site look nice, they should be used properly. The graphics should always be optimized for web use, and you should never use html to shrink your images. This will make your page sizes smaller, and they will load quicker. Another technique is to use tiled images whenever possible.

9. Using too much code

There are many tools out there that will generate code for you. However, these tools usually create more code than is necessary. This will make you page sizes larger, as well as make it difficult to update later. Minimizing the amount of code used, will make your site load quicker, and allow for faster updates and alterations later.

10. Opening New Browser Windows

Users hate unwarranted pop-up windows. Links that don't behave as expected undermine users' understanding of their own system. A link should be a simple hypertext reference that replaces the current page with new content. The strategy is self-defeating since it disables the Back button which is the normal way users return to previous sites.