It would be nice to have possibility to customize compiler's look&feel.

1l [digit "one" and small letter L]
0O [digit "zero" and capital o]

At least two things:

• font family (Courier is unreadable and was good few years ago. We have much better monospace fonts at the moment... even in Windows - just ask any frontend developer)
• font size (one size doesn't fit all)

As a bonus:

• color scheme of syntax highlighting (including background color)

It would be just one extra CSS file to load.

Maybe let the user to choose one of the predefined themes and an option to customize it and save?

I concur. You gotta do this! :)

Can't live without a black background and reasonable font size.

I concur as well!!! And folders!!!!!! =D

In my firefox there is a plugin that allows to zoom web pages. Just right click next to empty area of main.cpp text then zoom with the mouse wheel.

There's no reason any modern IDE shouldn't allow the user to chose the color scheme/theme. Color configurability should be integral in it's design. Period.