What not to do

Before you start any web project, having a good understanding of the most common mistakes to avoid can save you a lot of time and money. So here you go: By no means a definitive list, but certainly a good start for things to keep an eye out for.

Lack of direction

Before you start, you need a plan. Figure out what your site needs to do, who the audience is, how they will accomplish your objectives, and where they will be coming from (connection speed, browser, device, etc.). Without this information you're just guessing.

Poor usability

This piece of advice is very broad. But with a cursory understanding of your audience you can avoid the majority of these common sense mistakes:

• Font size too small and/or not of a web-friendly font family.
• Having content that is not web-friendly. I.e. not scannable, overly wordy, verbose, etc.
• Avoiding conventions. Hyperlinks should be underlined, navigation should be along the top or down the left, headings should be bold, highlighting should be used sparingly, etc.
• Using Flash for anything other than multimedia.
• Using PDFs to display content. If it's web content, put it in a web page.
• Slow page load times. I.e. unoptimized images, tables used for layout, overuse of multimedia, etc.

All of these will contribute to poor usability, which will in turn contribute to poor performance of your website.

Picking the wrong provider

Here; read this article; How to Choose a Web Designer. You need to make sure you're working with the right person for you, and for your project. If you don't, you'll end up with a finished product that does not accomplish what you need it to.