Validation: What? Why? How?

Paul Boag

Whether you are building your organisations web site yourself or whether you are using a team of web designers to do it for you it is important that the web pages which are built validate. But what is validation? Why is it important and how do you check for it?

What is validation?

Validating your web pages is about checking that they are correctly written. The pages are checked against a number of rules to identify any errors or non standard code. These rules are defined by the W3C who is responsible for setting the standards for web development.

Why is it important to validate your web pages?

There are a number of good reasons for making sure your web site is written in valid markup:

  • If your markup has errors in it then it might not appear correctly on all browsers. Just because it looks ok on your machine doesnt mean it will be so for everybody
  • Well written markup is more likely to be compatible with future technologies
  • Well written markup will appear quicker in your browser because the software that renders the web page won’t need to work around mistakes in the code
  • Poorly written markup often does not perform as well in search engine rankings
  • Well written markup is more likely to be compatible with related technologies such as Javascript or CSS

How do you validate your web pages

There are a number of automated tools out there which will check your markup for you. Probably the most widely used is the one developed by the W3C themselves. However today many web site development packages such as Macromedia Dreamweaver has validation software built in.

My personal favourite at the moment is an extension for Mozilla Firefox called HTML Validator which appears as a small icon below the main browser window. Surf to a page you wish to validate and you either get a green cross if it validates or a warning sign if it doesn’t. This is easy to use and allows you to be constantly checking pages for validation while surfing the web.