<html><head><style> div.container{width:30em;border:1em solid;}div.box{box-sizing:border-box;box-sizing:border-box; /* Firefox */width:50%;border:1em solid red;float:left;}</style></head><body><div class="container"><div class="box">This div occupies the left half.</div><div class="box">This div occupies the right half.</div></div></body></html>