Edit in JSFiddle

    if(!$.support.placeholder) { 
        var active = document.activeElement;
        $(':text').focus(function () {
            if ($(this).attr('placeholder') != '' && $(this).val() == $(this).attr('placeholder')) {
                $(this).val('').removeClass('hasPlaceholder');
            }
        }).blur(function () {
            if ($(this).attr('placeholder') != '' && ($(this).val() == '' || $(this).val() == $(this).attr('placeholder'))) {
                $(this).val($(this).attr('placeholder')).addClass('hasPlaceholder');
            }
        });
        $(':text').blur();
        $(active).focus();
        $('form').submit(function () {
            $(this).find('.hasPlaceholder').each(function() { $(this).val(''); });
        });
    }

input{margin:50px;}
.hasPlaceholder{color:#555;}

<form> 
    <input type="text" placeholder="foo bar" />
</form>