function SwitchPic(IMGNAME, IMGPATH)
{
    document.images[IMGNAME].src = IMGPATH;
}
function PreloadPic(IMGNAME, IMGPATH)
{
    IMGNAME     = new Image();
    IMGNAME.src = IMGPATH;
}


  PreloadPic('sn4_ro_0', '../images/common/top_f2.jpg');
  PreloadPic('sn4_ro_6', '../images/common/link_f2.jpg');
  PreloadPic('sn4_ro_5', '../images/common/mail_f2.jpg');
  PreloadPic('sn4_ro_4', '../images/common/qa_f2.jpg');
  PreloadPic('sn4_ro_3', '../images/common/sekou_f2.jpg');
  PreloadPic('sn4_ro_2', '../images/common/jigyou_f2.jpg');
  PreloadPic('sn4_ro_1', '../images/common/company_f2.jpg');