var flipper = 0;

function show()
{
     flipper = Math.floor(Math.random()*11);

        if (flipper <=5)
        {
        document.getElementById("div_left").innerHTML='<img border="0" width="267" alt="" src="gruppe1.png">';
        }
        else
        {
        document.getElementById("div_left").innerHTML='<img border="0" width="267" alt="" src="gruppe.png">';
        }
}

function rotate()
{
if (filpper == 0){
document.getElementById("div_left").innerHTML='<img border="0" width="267" alt="" src="gruppe1.gif">';
flipper =1;
}
else
{
document.getElementById("div_left").innerHTML='<img border="0" width="267" alt="" src="gruppe.gif">';
flipper = 0;
}
}