var goto_top_type = -1;
var goto_top_itv = 0;

function goto_top_timer() {
 var y = goto_top_type == 1 ? document.documentElement.scrollTop : document.body.scrollTop;
 var moveby = 15;

 y -= Math.ceil(y * moveby / 100);
 if (y < 0)
 y = 0;

 if (goto_top_type == 1)
 document.documentElement.scrollTop = y;
 else
 document.body.scrollTop = y;

 if (y == 0) {
 clearInterval(goto_top_itv);
 goto_top_itv = 0;
 }
}

function goto_top() {
 if (goto_top_itv == 0) {
 if (document.documentElement && document.documentElement.scrollTop)
 goto_top_type = 1;
 else if (document.body && document.body.scrollTop)
 goto_top_type = 2;
 else
 goto_top_type = 0;

 if (goto_top_type > 0)
 goto_top_itv = setInterval('goto_top_timer()', 50);
 }
}