If you followed a link to http://davehart.net/jpg-links-unsafe.jpg and expected a relatively "safe" image to appear, then this webpage might surprise you. As you probably can see in you web browser's "address bar" above, you have been redirected to http://davehart.net/jpg-links-unsafe.jpg/ which is a silent alias within the webserver for a default document, in this case http://davehart.net/jpg-links-unsafe.jpg/index.html. This does not require any special configuration on the webserver, because it is standard behavior to redirect references to directories (folders) which lack the trailing slash (/).
Why does this matter? Sometimes people browse pictures using web browsers which are vulnerable to malicious websites, believing they are safe if they only browse .jpg URLs, which must be pictures after all. That is the point behind publishing this page.
Be careful what you assume. Cheers. Here's a pic in case that's what you were hoping for.