css divide width 100% to 3 column

Question

I have a layout where I have 3 columns.

Therefore, I divide 100% by 3.

The result is obviously 33.333....

My goal is perfect

Answer 1

A perfect 1/3 cannot exist in CSS with full cross browser support (anything below IE9). I personally would do: (It's not the perfect solution, but it's about as good as you'll get for all browsers)

#c1, #c2 {
    width: 33%;
}

#c3 {
    width: auto;
}