I want to have my round div to keep the text inside it. like you see on the image

I've created an example of how you can achieve this. There is not an easy way yet, but it's coming in the near future as Spudley mentioned. http://jsfiddle.net/kUJq8/5/
This example is based on the same concept used by http://www.csstextwrap.com but I created this example to explain what's going on and how to achieve this effect.
Basically, you need to create your circle first and some sample text, then create a set of "imaginary" floating div's to give your text guidelines to not exceed and automatically wrap to the next line. Feel free to play around with the widths of the div's so you can achieve the desired effect. Also, if you remove the border, you can see what the text actually looks like. The border helps when setting the widths of the div's.
In my example, I didn't create the whole circle, but it should be enough to get you going on the right track. Please let me know if you need any further assistance with this idea. Thanks.