HTML site verification tool

Question

I need an online tool, in which I just enter an HTML website's URL and it gives me the list of issues in it. What type of issues I need to check are:

1. 404 error and other errors like this.
2. HTML5 compatibility issues like this tag is no more being used in HTML5 and other errors like this.
3. CSS issues.
4. Any other issues related to HTML websites standards.

Answer 1

You should try this validation tool from W3C.

http://validator.w3.org/