Images with rounded corners
css, html, javascript
Solution
It's using an image overlay that contains the curved borders.
<img class="rounders2_img" width="103" height="80" alt="" src="http://pad2.whstatic.com/images/thumb/1/18/Shadow-of-a-Writing-Hand-1834.jpg/-crop-103-80-103px-Shadow-of-a-Writing-Hand-1834.jpg"/>
<img class="rounders2_sprite" src="http://pad1.whstatic.com/skins/WikiHow/images/corner_sprite.png" alt=""/>
The same technique is used generally for drop shadows.
This is done because IE doesn't support many CSS 3 cool stuff, like rounded corners:
moz-border-radius: 5px; -webkit-border-radius: 5px;
Problem
How do sites like these get to display images with rounded corners? I checked with Firebug that the image being downloaded has sharp corners but the image being displayed has been modified somehow. EDIT: I am referring to the rounded thumbnail pictures seen in the "Featured" articles section on the site mentioned.