Using Mozilla FireFox? , making use of the Addons. Install the Html Validator Toolbar and the Web Developer Toolbar. from https://addons.mozilla.org. Also Install the XML Developer's Toolbar used to validate the XML code. After installing the tools we will create an html page. Once the html page is created we will validate it using html validator. Fix the errors if validator gives errors after html page validation. Once all the errors are removed, rename the html file to xhtml. In this xhtml file change the document type to xhtml and leave the syntax the same. Again get it validated and in case of errors get try to fix the errors. By performing the above mentioned process, we will come to know about different errors, warnings and their fixes. Html validation will be of great help in writing a webpage and in learning the use of tags, html syntax and we will get a chance to compare the DTD for HTML and XML.