I often take screen prints of things I find on the web that I want to incorporate into my books. On my iPad I am constantly taking screen print 'photos' of articles, recipes, fun things I see on Facebook.
When you do a screen print, it results in a .PNG file which is recognized as a photo in most of the photo software that is downloaded on your computer such as Blurb and iPhoto.
However, many of the web based applications ask for a .JPG file and you'll see that when you try to load a .png file up into their services, that they are grayed out.
This is no big deal. It's very easy to convert a file from one format to another with software already on your computer.
1. Open the photo: For PCs use Paint, for MAC use Preview
2. Select File Save / Save As and choose the JPG type extension
3. Save the file