//ロールオーバー

BlogImgOut  = new Image();
BlogImgOut.src  = "image/blogbanner.jpg";
BlogImgOver = new Image(); 
BlogImgOver.src = "image/blogbanner_ro.jpg";

function myMouseOutBlog(){
  document.BlogImg.src = BlogImgOut.src;
}
function myMouseOverBlog(){ 
  document.BlogImg.src = BlogImgOver.src; 
}