Html&css what next?

hey i know a good number of html tags and css and how to use it and some cool things but i am wondering whats next? i wonna be a web developer whats next? what the language i have to cover now i can do a little bit of skeleton and styling to the page do i have to learn java-script and php to make it interactive what is teh most important thing to do now i am not waiting for instructions iam just waiting for an advice and i thank every one who will reply and i know some php code too an d i know python can i use python in web development