Sometimes when I view an image (just an image, something like
http://www.example.com/blah.jpg), it sometimes opens up the image and other times I am asked which program I want to use to view the file.
Why is that?
This is usually configured on the host site.
Sometimes the host wants to force the download as shown in this example here.
It has something to do with the mime-type being sent by the web-server not matching the extension for that mimeType on your computer.
i don't know the specifics. i've looked into it a few times in the past; but i've forgotten.
But it can be the fault of a mis-configured web-server; sending you a .jpg when with a Content-Type of image/gif.