function installExtension(aEvent, extensionName, iconURL) {
   var params = new Object();
   params[extensionName] =
	    { 
		URL: aEvent.target.href,
		IconURL: iconURL,
	        toString: function () { return this.URL; }
            };

   var res = InstallTrigger.install(params);
   if (!res) { 
	alert("If you see an error bar at the top of your browser, follow these instructions:\n" +
		"1. Click the \"Edit Options...\" button on the error bar.\n" + 
		"2. Click the \"Allow\" button in the dialog box that appears.\n" + 
		"3. Click \"OK\" to confirm and close the dialog box.\n" + 
		"Now you can install extensions from this site.\n" +
		"Click the install link again to install the extension.\n\n" +
		"If you don't see the error bar, please make sure you have enabled \n" + 
		"extension installation from Web sites in the \"Options\" dialog."
 		);
   }

   return false;
}