I have seen many blogs showing nice glossy borders around the images and i liked them. The problem is i have blog with over 300 posts and i want to add border to image automatically and i didnt know how to do it. It seems to be the simplest of the problem and couldnt crack the nut!
Finally i was able to add images by making a few changes in styles.css in the current wordpress theme. All you have to do is specify the border and background. 
Just open styles.css in your wordpress theme and put this code.
[php]
<blockquote>
<pre>/* This will add border only to featured images.*/
.post img { background: #f3f3f3; border: 1px solid #e7e7e7; }
/* This will add border to images and you will see a image holder with background set */
.post p a img { background: #f3f3f3; padding: 10px; border: 1px solid #e7e7e7;}
</pre>
[/php]
