function newImage(arg) {
         if (document.images) {
                 rslt = new Image();
                 rslt.src = arg;
                 return rslt;
         }
 }

 function changeImages() {
         if (document.images && (preloadFlag == true)) {
                 for (var i=0; i<changeImages.arguments.length; i+=2) {
                         document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
                 }
         }
 }

 var preloadFlag = false;
 function preloadImages() {
	if (document.images) {
		buttons_about_over = newImage("images/buttons_about_over.gif");
    buttons_bricks_over = newImage("images/buttons_bricks_over.gif");
		buttons_pavers_over = newImage("images/buttons_pavers_over.gif");
		buttons_econblocks_over = newImage ("images/buttons_econblocks_over.gif");
		buttons_rooftiles_over = newImage("images/buttons_rooftiles_over.gif");
		buttons_projects_over = newImage ("images/buttons_projects_over.gif");
    buttons_help_over = newImage("images/buttons_help_over.gif");
		buttons_contact_over = newImage("images/buttons_contact_over.gif");
		preloadFlag = true;
	}
}