The most important part of web design is defining the purpose of your web site. Is it to promote your company?, is it to sell your product?, are you creating a site to enable you to share information about your favourite hobby or pastime?

There are so many uses for a web site, if you yourself are not really sure what your web site is about, then visitors to your site will have no idea what the site is for and will have no reason to return. This would be disastrous if you are hoping to make money from your web site

Don't go into lengthy explanations. You should be able to define the purpose of your web site in one simple sentence. You definitely don't need a mission statement like those that you see on some web sites. In fact, no web site should need a mission statement.

Visitors should be able to tell from viewing your first page or two what your web site is about. Let's face it, if your site needs a a lengthy description to justify it being there, then your site isn't doing its job and you should probably go back to the design stage and start again.

From my personal experience, sites with mission statements appear to be trying to justify the prices that they are charging for their product or service. The higher the charge, the longer the mission statement.

Let me give you a couple of examples.

The definition for the original version of this web site was

That was it, that was all that I needed to go on to the next stage.

Now that I have broadened the scope of this site and have started to submit it to the search engines, I have changed my definition to

That's it, 22 words. That is all I needed to go on to the next stage.

You should be able to define the purpose of your web site in a similar manner, don't worry about the details, they come later. Once you have done that, you are ready to go on to the next stage