function A_Li(){
Sel=document.Link1.cnt.selectedIndex;
Ms=document.Link1.cnt.options[Sel].value;
parent.main.location.href=Ms;
}

<!--------------------preload_start-------------------->

preload_img=new Image();
preload_img.src='';

preload_img2=new Image();
preload_img2.src='';

preload_img3=new Image();
preload_img3.src='';

preload_img4=new Image();
preload_img4.src='';

<!--------------------preload_end-------------------->

<!--------------------window.open_start-------------------->

function subWin1(){
window.open('map_office.html','window2','resizable=1,menubar=1,directories=no,scrollbars=1,status=no,location=no,width=500,HEIGHT=430');
}

function subWin2(){
window.open('map_leokobe.html','window2','resizable=1,menubar=1,directories=no,scrollbars=1,status=no,location=no,width=500,HEIGHT=430');
}

function subWin3(){
window.open('map_leotokyo.html','window2','resizable=1,menubar=1,directories=no,scrollbars=1,status=no,location=no,width=500,HEIGHT=430');
}

function on(){window.focus();}
function closeWin(){parent.close();}

<!--------------------window.open_end-------------------->