jQuery.validator.addMethod("alphanumeric", function(value, element) {
	return this.optional(element) || /[-0-9a-zA-Z]/gi.test(value);
}, "Letters, numbers, spaces or underscores only please");  

jQuery.validator.addMethod("lettersonly", function(value, element) {
	return this.optional(element) || /^[a-z]+$/i.test(value);
}, "Letters only please"); 

jQuery.validator.addMethod("nowhitespace", function(value, element) {
	return this.optional(element) || /^\S+$/i.test(value);
}, "No white space please");