Web browsers may display "mixed content" warnings in the address bar when an HTTPS (secure) webpage contains images, iframes, or other resources from HTTP (non-secure) source URLs on other websites. This may cause the whole page to be delivered insecurely.
Copying an image to the clipboard and then pasting it into a page's Body box can cause severe problems for your website. The action of pasting the image from the clipboard inserts it into the code with a very long string of letters and numbers as its URL source, instead of a real URL.
Chrome and Internet Explorer prevent this action, but Firefox allows it.