Cool project! My only complain is it defaults font to Courier (monospaced) which is harder to read and takes more place. You might use ‘Georgia’ which is web safe and pretty legible. Or of course, Times New Roman (just like site on this post)
You're right, but I think this depends on the browser too. I actually pass a stylesheet in the HTTP response header to make text appear white on a black background. Firefox respects this, but Chrome doesn't (at least for plain text files):
Will have to test again when I get some time to see what the options are. Might be a bit of a hack as there really aren't any HTML elements to target, so it might be that Firefox applies the CSS after inserting the text into an HTML template.