div 可以输入 行高自适应，模仿微博回复

<div contenteditable="true" style="color:#00FF00;width:400px; min-height:20px; max-height:300px; _height:120px; margin-left:auto; margin-right:auto; padding:3px; outline:0; border:1pxsolid#a0b3d6; font-size:12px; line-height:24px; padding:2px; word-wrap:break-word; overflow-x:hidden; overflow-y:auto; border-color:rgba(82,168,236,0.8); box-shadow:inset01px3pxrgba(0,0,0,0.1),008pxrgba(82,168,236,0.6);">
</div>