Best way to represent 1/3rd of 100% in CSS?

Answer 1

The highest resolution screen is a non-production NEC LCD screen with a resolution of 2800x2100. Even at that size, one pixel is 0.0357% of the width of the screen. So 33.33% should be close enough until 5,000-pixel-wide screens become the norm.

John Resig did some research into sub-pixel rounding in different browsers, though, so depending on your three columns to equal exactly the width of the screen may never have a perfect solution.