JavaScript placeholder polyfill.

placeholder.js

function isPlaceholderSupported() {
    var input = document.createElement("input");
    return ('placeholder' in input);
}

var placeholdersupport = isPlaceholderSupported();

// find the elements that are advertising this behaviour
// then setup each one
$("[data-behaviour='placeholder']").each(function() {
    var placeholderText, elements, inputValue;
    element         = $(this);
    placeholderText = element.attr('placeholder');
    inputValue      = element.attr('value');
    // use the input value if present instead of the placeholder
    if (inputValue != '') {
        placeholderText = inputValue;
    };
    // polyfill
    if (!placeholdersupport) {
        element.val(placeholderText);
        element.focus(function() {
            if ($(this).val() == placeholderText) {
                $(this).val('');
            }
        });

        element.blur(function() {
            if($(this).val() == '') {
                $(this).val(placeholderText);
            }
        });
    };
});