You can use a series of spans and 4 images, one for each corner, to make a resizable rounded corner div. Like this:
div {
background: white url(topleft.gif) top left no-repeat;
}
div span {
display: block;
background: url(topright.gif) top right no-repeat;
}
div span span {
background: url(bottomright.gif) bottom right no-repeat;
}
div span span span {
padding: 2em;
height: 0; /* fixes a padding bug in IE */
background: url(bottomleft.gif) bottom left no-repeat;
}
div span span > span {
height: auto; /* sets the height back to auto for all other browsers */
}
And now for the HTML:
<div><span><span><span>Round corners!</span></span></span></div>
For an actual example and code please refer to this page for a working example and source code.