Forget certification in html/xhtml/css they are barely even programming languages, they are a markup syntax.

Adobe help you get certified in adobe applications, the net does not revolve around adobe. The core applications and technologies that run the net have absolutely nothing to do with any adobe technology.

w3schools.com all you need to know.

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"I have not failed. I have found 10,000 ways that don't work" - Thomas Edison.
"The secret to creativity is knowing how to hide your sources" - Albert Einstein.