Changing the font - Firefox.

This isn't so much of a technological question, so feel free to move this thread if it's in the wrong place...

I just downloaded Firefox and am happy with it thus far. However, I am looking for the font which most resembles the most common font on Internet Explorer, my old browser.

Question 1: Which font should I use?

But when I change the font from, say, Arial to Courier New, nothing seems to change.

Question 2: Is this normal? If not, what should I do?

I believe that the font will only change from the about:config tweak if the websites that you visit do not specifically define a font to use. There may be another tweak around that, but it's generally not a good idea to use a non-default font on sites, because it may mess up the layout.

Tools > Options > Content > Fonts & Colors Advanced > uncheck "Allow sites to use their own fonts"