Help me with my new website!

[FlatAssembler]

In any event, like always, use the right tool for the job at hand.

Well, finding what's the right tool for the job isn't the easiest thing to do. Especially when you have, preparing for the programming competitions, read quite a few books about C++ that try to convince you all the other languages (especially C# and Java) suck.
Do you think C++ is really that good for algorithms, data structures and string manipulation as it's portrayed to be? Now it seems to me that it's one of the worst languages for those things. Have you ever tried to use Emscripten? What do you think about it?

IE6 is dead. Let it die, and move on. Nobody has it except you, and nobody should.

Well, almost everyone who has Windows XP has it (along with a few better browsers). Most of the Internet forums even today appear to work just fine in it.
Besides, the NetFront browser on my old Samsung SGH-E840 appears to behave just like Internet Explorer 6. When it comes to JavaScript, it appears to support basic DOM manipulation and alerts, yet it fails to even run the Acid3 test or HTML5 test.
I am not trying to make my website look the same in simpler browsers, I am trying to make the text readable in simpler browsers. That is something to be expected, right?

I don't know exactly what you are trying to do.

I am trying to do this (but not that it's triggered on click, but on hovering):
https://www.w3schools.com/howto/howto_js_popup.asp
However, the solution they present depends on the container for the pop-up being absolutely positioned. I can't make the container absolutely positioned if it has to be scrolled to in the "main" (which has overflow:auto).

I anticipate that you won't want to use unnecessary bandwidth for jQuery.

No, I just don't see how it would help exactly.