Wordpress removes code from posts, how to solve the problem?

Question

css

I've been struggling with an incomprehensible problem since morning. It is necessary to make code highlighting in articles on the blog.
Found the best option here: avovkdesign.com/podsvetka-sintaksisa-highlightjs.html Posted
on the blog. And everything seems to be fine, but if I insert the code starting with "script" - nothing is displayed. It's like there's just no text.
You can see it here: blog.sk8er.name/rabota/podgotovka-sajta-k-novomu-godu In the article, I showed the code starting with "script" 2 times, where the problem is clearly visible.
Below there is another insert with css, it shows that everything works, but the problem is only with "script".
How to be? I don’t even know where to dig and what to google.