placeholder shim
测试使用漂浮的label标签来弥补placeholder功能
by lmk123
HTML
<input id="test" placeholder="测试">
JavaScript
var $test = $('#test');
var h = $test.outerHeight();
var w = $test.outerWidth();
var offset = $test.offset();
var $label = $('<label for="'+$test[0].id+'">'+$test.attr('placeholder')+'</label>').appendTo('body');
$label.css({
width:w,
height:h,
position: 'absolute',
zIndex:1,
left: offset.left,
top: offset.top,
cursor: 'text'
});