var box = new Array();
box[0] = 'div1';
box[1] = 'div2';

function show(id)
{
        if(document.getElementById(id).style.display=="none")
        {
                for(i=0;i<box.length;i++)
                {
                        document.getElementById(box[i]).style.display="none";
                }

                document.getElementById(id).style.display="block";
        }
        else
        {
                document.getElementById(id).style.display="none";
        }
}
window.setTimeout("show('div1')", 5000);
window.setTimeout("show('div2')", 10000);