function populateElement(selector, defvalue) {
    if($.trim($(selector).val()) == "") {
        $(selector).val(defvalue);
    }
  
    $(selector).focus(function() {
        if($(selector).val() == defvalue) {
            $(selector).val("");
        }
    });
    
    $(selector).blur(function() {
        if($.trim($(selector).val()) == "") {
            $(selector).val(defvalue);
        }
    });
 }

$(function() {
	populateElement('.email', 'email address');
});