I want to code a blog system. What language?

What coding language would I need to learn to code a blog system?
PHP? ASP? What are blog systems (like livejournal, blogger.com, etc) usually coded in?

Why I want to learn coding: to code a dynamic blogging system that supports "categories" (basically, tagging of blog entries), cause I haven't seen one anywhere..

about me: I'm an absolue newbie at coding. Did some HTML back in 1997. (And no..you won't see me post about my mood and what song I'm listening to, so please help!)

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