如何让文本出现在下一行，而不是溢出？

我在我的页面包含文本的固定宽度div。当我输入一长串字母时，它溢出。我不想隐瞒溢出我要显示在新的一行溢出，见下图：

I have a fixed width div on my page that contains text. When I enter a long string of letters it overflows. I don't want to hide overflow I want to display the overflow on a new line, see below:

<div id="textbox" style="width:400px; height:200px;">
dfssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssfddddddddddddddddddddddsdffffffffffffffffsdffffffffffffffffdfssssssssssssdf
</div>

反正有禁用溢出并把四溢的文字在新行？微博确实是这样，但我不能用CSS弄清楚它可能他们正在使用的JavaScript。

Is there anyway to disable overflow and put the overflowing text on a new line??? Twitter does something like this but I can't figure it out with CSS it's possible they are using Javascript.

任何人都可以用这张??

Can anybody help with this??