Can you give mor details? Without more information is not possible to give you an answer about your question
W3C is a website dedicated to helping webmasters program efficiently. They have an html validation tool that scans a page that you link to it. This tool verifies that the page is free of errors and bad practices. If it finds errors, it reports them to you and explains the problem. Generally, webmasters want their website to perform well on all devices and this tool helps you every step of the way. The tool can be found here: http://validator.w3.org/
Hello, W3C is for world wide web Consortium it is basically a rule book through which users can check HTML and XHTML documents for well formed markup or it define how to write a well form CSS, javascript, HTML to make sure we are doing our work in correct way. Thank you.