The two styles differ in various ways, but the important differences are:
WTF Tournament fighting requires full body armour, and the combatants can use full contact on the allowable target areas. Strikes to the body with closed fists & strikes to the body & head with the feet. ITF Taekwondo uses a semi contact system for competition without full body armour.
WTF comes from South Korea, ITF is practised in North Korea, although it's headquarters are in Canada.
The patterns are totally different. If you're training in, or thinking of training in ITF Taekwondo, the patterns on this site will not help you a lot with your training, but will give you an insight into the WTF side of things which cannot hurt.
I should point out that I have the utmost respect for the ITF style. Some people are of the opinion that ITF is more useful than WTF from a self defense point of view. I don't know, and sincerely hope I never get into a situation that forces me to find out how effective my training has been outside the training hall or a competition.
Steve Conway has some excellent tips on ways to improve your training on his taekwondo site, and the content is written in a humorous and easy to understand tone. Highly recommended!
There are some great Taekwondo articles Colin Wee's Traditional Taekwondo site.
The site is done using HTML & CSS. It was using Javascript before, but I wanted to make the site easier to navigate and create valid code. My personal thanks to Stu Nicholls. Visit him for CSS tutorials if you're looking to learn (or improve on) how to create some spectacular (I'm not claiming mine are!) pages using valid code without having to resort to Javascript, Flash or any other such tricks.
Yours in Taekwondo
Andy "Tomcat" Fletcher