$(':checkbox') is equivalent to $('[type=checkbox]'). As with other pseudo-class selectors (those that begin with a ":") it is recommended to precede it with a tag name or some other selector; otherwise, the universal selector ("*") is implied. In other words, the bare $(':checkbox') is equivalent to $('*:checkbox'), so $('input:checkbox') should be used instead.
').parent().css({background:"yellow", border:"3px red solid"});
$("div").text("For this type jQuery found " + input.length + ".")
.css("color", "red");
$("form").submit(function () { return false; }); // so it won't submit
]]>