isIE = document.all;
popupbox = document.getElementById("popup_box");
pos_x = (screen.width - 400)/2 + 160;
popupbox.style.left = isIE ? pos_x : pos_x + 'px';

function popup_elrejt ( )
	{
	popupbox.style.visibility = "hidden";
	}

function popup_megjelenit ( )
	{
	popupbox.style.visibility = "visible";
	}

function popup_beuszas ( offset_y, sebesseg )
	{
	pos_y = parseInt(popupbox.style.top);
	popupbox.style.top = isIE ? pos_y + offset_y : pos_y + offset_y + 'px';
	if (pos_y < (15)) setTimeout("popup_beuszas ( "+offset_y+", "+sebesseg+" )", sebesseg);
	}

popup_megjelenit ( );
popup_beuszas ( 10, 0 );