var classStr = document.body.getAttribute("class") || document.body.className;;
var classNames = classStr.split(/\s+/);

for(var i = 0, cl = classNames.length; i < cl; i++){
	var targetItem = document.getElementById("gnavi_" + classNames[i]);
	if(targetItem!=null){
		targetImg = targetItem.childNodes[0].childNodes[0];
		targetImg.setAttribute("src",targetImg.getAttribute("src").replace(/^(.+)(\.[a-z]+)$/, "$1_fs$2"))
	}
}