In recent times HTML and CSS validation has become a hot topic in webmaster circles, with many points of view on its importance and the correct approach to take, when creating search engine friendly websites.  In the below article on HTML and CSS validation, I will touch on a few different perspectives and attempt to provide you with my best practise approach to HTML and CSS validation.

What is HTML & CSS Validation?

HTML and CSS validation is the process of checking the web pages that you have created for errors using a software application or online service that inspects the code behind each page, ensuring that you use the correct syntax.

HTML Validators

An HTML validator checks your HTML code and ensures that it is in compliance with the standards as set out by the W3 Consortium.  There are a variety of validators available, some you can use for free while others are for commercial use only, some just inform you of your errors while others suggest possible fixes.  Try the free W3 Consortium online validator to validate your HTML pages at: http://validator.w3.org/.

CSS Validators

As you might expect, a CSS validator checks your Cascading Style Sheets for correctness.  A CSS validator checks your CSS code ensuring that it complies with the CSS Standards as set out by the W3 Consortium.  Some of the more advanced CSS validators will even inform you if you are using features that are not compatible with certain browsers.  Use the free W3 Consortiums CSS validator at http://jigsaw.w3.org/css-validator/.

Why Validate HTML Code

The webmasters who promote HTML and CSS validation offer a variety of reasons why you should validate your code.

Cross-browser & Cross-platform Compatability

Having created a web page, you will open it in your favourite browser and although it may look great, when someone else looks at it with a different browser the page may not load correctly.  This is usually as a result of a syntax error in your HTML or CSS code.  Had you run your page through the HTML and CSS validation, you would have found and corrected the error.  Additionally, ensuring that your pages are validated, provides you with the assurance that when the browser developers release updated versions of there browsers, your web page will still render correctly.

Search Engine Visibility

Browsers compensate for syntax errors in different ways, some will try to make an assumption as to what the correct page should look like and render it accordingly, while other browsers will simply ignore the broken element.  Now when a seach engine finds your broken page and tries to index it for keywords, it is faced with the same problem, some search engines will choose to stop indexing your page at the error, if the error is near the top, this may result in your page not being indexed at all.  HTML and CSS validation would resolve this.  More information on this topic is available in my article, Why is my website not ranking in the search engines??

Professionalism

Apart from the two reasons above, having syntax errors in your web pages shows that either you don't pay attention to detail, or you don't know what you are doing.  Errors on your web pages reflect negatively on your abilities and will affect your marketability as a web developer.

Why Not Validate HTML Code

Web masters who choose not to use HTML and CSS validation usually provide these reasons.

Validation Does Not Gaurantee Compatability

HTML and CSS validation does not gaurantee that your page will display correctly in all browsers, you still need to check your web pages for browser compatability.

Time Constraints

Most webmasters and website administrators have hundreds or thousands of web pages.  To validate and make the necessary changes would be very time intensive and they argue that if these pages are already out there and performing adequately, thier time would be better spent on productive work.

Visitors Don't Check Source Code

The last counter arguement to validation and professionalism, in particular, is the premis that most site visitors are only interested in the content of your web pages and won't go digging around in the code, looking for errors.

Best Practise Solution

By the time I first learnt about HTML and CSS Validation, I already had thousands of pages out on the Internet.  I quickly worked out that it would take me over 400 hours to validate and correct all these pages, time that I just did not have available to me.

I decided to committ to my clients that all new pages and all updated pages would be validated and corected, but old pages would not be validated until they were updated.  This has worked well for me and I believe it to be the best practise solution when it comes to HTML and CSS Validation.

How Often Should I Validate?

Some web master vadidate each time they make a change, while others only validate when they make a major change.  As a rule I validate each time I make a template change, regardless of how small.  I will also always validate if there is anything other than plain text in an article as most WYSIWYG editors are renowned for messy code.

HTML and CSS Validation has many benefits, ensuring that your code is free of syntax errors and assisting with the pages readability to both the search engines, browsers and future updates to both.