Help with Javascript to move a span to left and top position for Firefox

//The code calling the function is here
<map name="testMap">
   <area onMouseover="showByLink('img3','nameLayer',this,-500,30)" onMouseout="hide('nameLayer')" shape="circle" coords="282,326,4"/>
</map>
 
//The function is here
<SCRIPT LANGUAGE="JavaScript"><![CDATA[
	function showByLink(imgName, object,link,x,y) {	
		img=eval(imgName);
		document.county.src= img.src;
 
//Added this for Firefox but not working
		var browser = window.navigator.userAgent
		if(browser.indexOf("Firefox") > 0) {
			var c = document.getElementsByTagName("body")[0].getElementsByTagName("*");
		
			if(c){	
				c[object].style.visibility = 'visible';
				if (c[object].myFlag == null) {					
					c[object].style.left = link.x + x;
					c[object].style.top = c[object].offsetTop + y;
				}
				c[object].myFlag = true;
			}
		}
		else{							
			if (document.layers && document.layers[object]) {
				document.layers[object].left = link.x + x;
				document.layers[object].top = link.y + y;
				document.layers[object].visibility = 'visible';
			}
			else if (document.all) {
				document.all[object].style.visibility = 'visible';
 
				if (document.all[object].myFlag == null) {
					document.all[object].style.posLeft = document.all[object].offsetLeft + x;
					document.all[object].style.posTop = document.all[object].offsetTop + y;
				}
				document.all[object].myFlag = true;
			}
		}
	}