Board Thread:General Discussion/@comment-4059391-20130825005803/@comment-4519283-20130918214107

It sounds like it does have an extension. If it didn't have an extension, it wouldn't open up in preview, because the Mac wouldn't know what to do with it. Here's how to check the file extension: Try checking the Javascript Console, do this by: Repeat the instructions but unchecking Show Develop Menu to hide it.
 * 1) Open Terminal (click the magnifying glass in the top-right, type Terminal, click Terminal)
 * 2) Type: defaults write com.apple.Finder AppleShowAllFiles TRUE
 * 3) Type: killall Finder
 * 4) Now check the file, it should say ai.xxx (the xxx being the file extension)
 * 5) To turn it off, go to the terminal and type defaults write com.apple.Finder AppleShowAllFiles FALSE
 * 6) Then killall Finder
 * 1) Typing command-comma (or go to Safari=>Preferences)
 * 2) Under Advanced, check Show Develop Menu
 * 3) Close the Preferences window
 * 4) Under Develop, press Show Error Console
 * 5) Refresh the page