You can do this by adding a style information to the img tag. So if you're using the wordpress editor you'll see something like:
img src="wp-content/uploads/2010/05/your-image.jpg" alt="" title="" class="alignnone size-full wp-image-74"
add style="border: 5px;" to this tag (change the value of 5px to any value you like) - it should look like this:
img src="wp-content/uploads/2010/05/your-image.jpg" alt="" title="" class="alignnone size-full wp-image-74" style="border: 5px;"
If you've many images you want to display with a border you can also define a class in the stylesheet ( filename extension .css). The syntax should look like this:
.image-border {
border: 5px;
}
Now if you want to display an image with a border just add the class image-border to the image. You don't need the style information anymore.
img src="wp-content/uploads/2010/05/your-image.jpg" alt="" title="" class="alignnone size-full wp-image-74 image-border"
If you want a colored border just add this value to your stylesheet definition or to the style="" tag.
Example:
.image-border {
border: 5px;
border-color:#00ff00;
border-style:solid;
}
The Dude