CSS calc not working in Safari and fallback

The way I solved this problem, is introducing a pure CSS fall-back, that older browsers that don’t support CSS calc would only read.

figure.left {
    width: 48%;
    width: -webkit-calc(50% - 20px);
    width: -moz-calc(50% - 20px);
    width: calc(50% - 20px);
}

The left and right panels, get a width of 48% if the browser cannot read the calc values.

figure.logo {   
    min-width: 40px;
    width: 4%;
    width: -webkit-calc(40px);
    width: -moz-calc(40px);
    width: calc(40px);
}

And the logo, which sits in-between the two panels, gets a width of 4%. And also a minimum width of 40px. And if the calc values can be read by the browser, they are 40px.