Split Div Into 2 Columns Using CSS

Question

I have been attempting to split a div into two columns using CSS, but I have not managed to get it working yet. My basic structure is as follows:

Answer 1

Best way to divide a div vertically --

#parent {
    margin: 0;
    width: 100%;
}
.left {
    float: left;
    width: 60%;
}
.right {
    overflow: hidden;
    width: 40%;
}