if (document.images) {            // Active Images
            img1on = new Image();      
            img1on.src = "images/ln_about_on.gif";
			
			img2on = new Image();      
            img2on.src = "images/ln_submit_on.gif";
						
			img4on = new Image();      
            img4on.src = "images/ln_tips_on.gif";
			
			img5on = new Image();      
            img5on.src = "images/ln_alt_on.gif";
			
			img6on = new Image();      
            img6on.src = "images/ln_groups_on.gif";
            
            img7on = new Image();      
            img7on.src = "images/ln_resources_on.gif";
            
            img8on = new Image();      
            img8on.src = "images/ln_links_on.gif";
            
 
            

            img1off = new Image(); 
            img1off.src = "images/ln_about_off.gif";
			
			img2off = new Image(); 
            img2off.src = "images/ln_submit_off.gif"; 
					
			img4off = new Image(); 
            img4off.src = "images/ln_tips_off.gif";
			
			img5off = new Image(); 
            img5off.src = "images/ln_alt_off.gif"; 
			
			img6off = new Image(); 
            img6off.src = "images/ln_groups_off.gif"; 
            
            img7off = new Image(); 
            img7off.src = "images/ln_resources_off.gif"; 
            
            img8off = new Image(); 
            img8off.src = "images/ln_links_off.gif";           
            
                                      }

// Function to 'activate' images.
function imgOn(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "on.src");
        }
}

// Function to 'deactivate' images.
function imgOff(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "off.src");
        }
}

<!--browser launch begin-->
	var ie = "Microsoft Internet Explorer";
	var nn = "Netscape";
	var browser = navigator.appName;
	var version = navigator.appVersion;
	var mac = "MacPPC";
	var os = navigator.platform;

	function launchBrowser(url, name, width, height) {
		var x = 0;
		var y = 0;
		if(navigator.appVersion.length > 0 && navigator.appVersion.charAt(0) > '3' && navigator.appVersion.charAt(0) <= '9') {
			
			if(width > screen.availWidth - 12) {
				width = screen.availWidth - 12;
			}
			if(height > screen.availHeight - 30) {
				height = screen.availHeight - 30;
			}
			x = (screen.availWidth - 12 - width) / 2;
			y = (screen.availHeight - 30 - height) / 2;
		}
		var params =  "resizable=yes,scrollbars=yes,location=no,status=no,toolbar=no,menubar=no,directories=no,screenX=" + x + ",screenY=" + y + ",width=" + width + ",height=" + height + ")";
		var windowvar = window.open(url, name, params);
		windowvar.focus();
	}
<!--browser launch end-->
	function openLogon(){
		var url = "ep_login.php?op=login";
		var login = document.loginForm.login.value;
		var password = document.loginForm.password.value;
		var name = 'EPTM';
		url = url + "&login="+login+"&password="+password;
		launchBrowser(url,name,920,920);
	}