div
{
display:-moz-box; /* Firefox */
display:-webkit-box; /* Safari and Chrome */
display:box;
width:300px;
border:1px solid black;
}

#p1
{
-moz-box-flex:5; /* Firefox */
-webkit-box-flex:5; /* Safari and Chrome */
box-flex:5;
background:#f60;color:#fff;
}

#p2
{
-moz-box-flex:2.5; /* Firefox */
-webkit-box-flex:2.5; /* Safari and Chrome */
box-flex:2.5;
background:#690;color:#fff;
}