However good you are as a programmer, this doesn`t mean you never make mistakes, so a tool like CSE HTML Validator Lite is always a good idea. It checks and detects errors in your source code.
Some of the features of CSE HTML Validator Lite are: you can check the source code to detect errors, automatically change all the tags and attributes to lower case, add notes of interest to the attribute values, change the headers/footers of each page with your own design created from the templates it has, etc.
Apart from editing HTML code, CSE HTML Validator Lite also lets you edit and check XHTML and CSS.