how can i force an outer div to expand to the height of its content?

how can i force an outer div to expand to the height of its content?

I have a div element called "content" and i have the height set to auto
because i want it to have the same height with the height of the paragraph
which is inside of the class "smt". But in the page you can see that the
div that says "this another div" is not beneath the div "container" and
the div "content" doesn't have a height. I search it everywhere and
nothing seems to solve my problem so far.
Any help would be appreciated!
here is the link of the page:http://mathiatis.com/index4.html
Thanks!