function SwapImage(ImgName, ImgSrc) {
document.images[ImgName].src=ImgSrc;
}

PreImg=new Array();
for(i=1; i<=7; i++) {
PreImg[i]=new Image();
}
PreImg[1].src="common/nav_01_o.jpg";
PreImg[2].src="common/nav_02_o.jpg";
PreImg[3].src="common/nav_03_o.jpg";
PreImg[4].src="common/nav_04_o.jpg";
PreImg[5].src="common/nav_05_o.jpg";
PreImg[6].src="common/nav_06_o.jpg";
PreImg[7].src="common/nav_07_o.jpg";