I have a div element with style attached:
.mypost {
border: 1px solid Peru;
font-family: arial;
margin: auto;
min-width: 700px;
width: 700px;
You could try using float:left; or display:inline-block;.
Both of these will change the element's behaviour from defaulting to 100% width to defaulting to the natural width of its contents.
However, note that they'll also both have an impact on the layout of the surrounding elements as well. I would suggest that inline-block will have less of an impact though, so probably best to try that first.