Images in website

Question

If you want copy an image in a web page to Microsoft word, you place the cursor on that image and right click the mouse button a menu will pop-up in that menu you can see "Copy image" click on that then copy the image in Microsoft word. This is we do to copy an image from web page to MS word.

But you can't copy some images in this way. Please tell me the reason and how to copy these images.