Validating html code
It also means test-driving it with friends, relatives, co-workers, and strangers.Everyone has a different system and way of working, so ask for others to test-drive your styles or themes before you make them public.
Debugging doesn't have to be scary though — the key to being comfortable with writing and debugging any programming language or code is familiarity with both the language and the tools. HTML is not compiled into a different form before the browser parses it and shows the result (it is ).Make sure your codes and styles validate across the board.That means they have to meet the "strict" standards set by the W3C Organization and pass a variety of validations for CSS and XHTML. Some only check CSS, others XHTML, and others for accessibility.Having an accessible website is also regarded as good web design practice.As you can see, having a validated website has its definite plus points.
The resources and articles on validation below will help you learn more about validating your web page.