Ideal column width for paragraphs online

There is nothing worse than coming across a website with paragraphs that span the width of your screen resolution. They are usually so hard to read, I don't even bother.

A lot of web designers use generic grid and column systems, but I don't feel these have been optimised for readability, they are more of design guide on general aesthetics.

I guess it comes down to words per line. Are the rules that apply to print media the same for screen media?

Are there any type of guidelines to help me size the width of paragraphs on the screen?

I want to take into consideration:

• Major web font faces (i.e. Arial, Verdana, Georgia, Times)
• A range font sizes (i.e. 8px-24px)
• Space between columns