Here are the 4 corner images (gifs) used.
Here is an example box with rounded corners. Here is an example box with rounded corners. Here is an example box with rounded corners. Here is an example box with rounded corners.
Here are the 4 corner images (gifs) used.
This example demonstrates a flexible sized box. There are 4 corner images, each placed as a background image on a different tag (some text tags and some divs). Try resizing the browser window.
This is one of many possible techniques.
The CCS styles for this example are located in the <head> tag of this page, so just view the page source code to see what's going on.