This is an simple technique that can be developed by everybody. Just answer the following questions.

Does the website work perfectly if you turn off the CSS?
Does the website work perfectly if you disable the JavaScript?
Does the website was diagram with tables instate of using CSS?
Is all the essential information in HTML?
If the site have an extra code, does the essential information is in HTML?
Does the website was build in Flash?
Does it have a hidden content?

In order to answer the questions (most accurately) download the following application:

Internet Explorer:
Internet Explorer Developer Toolbar

Firefox:
Web Developer 1.1.3

Source: Standardzilla