function show_tip(id) {    
//	   ScrWidth =  screen.width;  w = 2/3 * ScrWidth;  posx = ScrWidth/2  - 2 * w/4;
//	   ScrHeight = screen.height; h = 3/4 * ScrHeight; posy = ScrHeight/2 - h/3;
	  
	        obj = document.getElementById(id);
	        if (obj.style.display == "none") {
	            obj.style.display = "block";

/*	            
		obj.style.left = posx + "px";
	        obj.style.top  = posy + "px"; 
	        obj.style.width   = w + "px";
	        obj.style.height  = h + "px"; 
	            	           
	            if (navigator.appName == "Microsoft Internet Explorer") obj.style.position = "absolute";
	            else obj.style.position = "fixed";
*/	        }
	        else obj.style.display = "none";
	    }