var ns = (document.all) ? false : true;

function change_bg(id, image) {
	if (ns) {
		layerObject = document.getElementById(id).style;
	} 
	else {
		layerObject = eval(id + ".style");
	}
	
	layerObject.backgroundImage = 'url(' + image + ')';
}

function validate_required(field, alerttxt) {
	with (field) {
		if (value == null || value == "") {
			alert(alerttxt);
			return false;
		}
		else {
			return true;
		}
	}
}

function validate_email(field,alerttxt) {
	with (field) {
		apos = value.indexOf("@");
		dotpos = value.lastIndexOf(".");

		if (apos < 1 || dotpos - apos < 2) {
			alert(alerttxt);
			return false;
		}
		else {
			return true;
		}
	}
}

function preloadImages(images) {
	var preloaded = [];

	for (var i = 0; i < images.length; i++) {	
		preloaded[i] = document.createElement('img');
		preloaded[i].setAttribute('src', images[i]);
	}
}