The world wide web is full of badly designed web sites. If a web site isn't pleasant to view and navigate, then the visitor will leave. If this happens, the site has failed in its aims.

The problem is that while HTML is relatively easy to learn, design is an art form that cannot be mastered so quickly. Colour theory, balance and layout are just some aspects of web design. Added to that are the practical necessities of keeping download time low and ensuring that the site is visible to a maximum number of people.

Ignoring the subtleties of good web design, it's still amazing how many sites break the most basic aesthetic rules.

1. Incorrect spelling. Nothing interrupts the flow of text quite like a misspelt word.
2. Garishly clashing colours. You don't need to have an art degree to realize that bright red on bright green is not a pleasant combination.
3. Blinking text and flashing graphics. These effects are not impressive; they're annoying.
4. Haphazard navigation. I should be able to concentrate on the content of a web site and not constantly be thinking about how to navigate around it.
5. Minuscule text. This is hard to read.
6. Giant text. This is equally hard to read
7. Huge graphics. These will increase download time and encourage visitors to leave before the graphics are finished downloading.
8. Broken links. Nothing is more unprofessional than a link that leads nowhere.
9. Screenfuls of uninterrupted text. The web is not print. It's harder to read lots of text on a screen than on paper. Text needs to be laid out and broken down into bite sized sections.
10. Uninteresting and unoriginal content. The most basic and also the worst design flaw.

• Why do I need a web site?
• What makes a web site work?