Charles writes:

“Dear MacMedic: I downloaded and installed Firefox and put it in my dock but every time I restart my Mac the Firefox icon has a grey question mark over it and it won’t run! I have to go find Firefox again and drag the icon into the dock again. Why does this keep happening?”

Thanks for the question, Charles. I see this frequently and I bet I know what’s going on.

The problem is that you’re not actually installing Firefox into your Applications folder; you’re just running it from the disk image that it comes in. Let me explain.

When you download most Macintosh applications, including Firefox, you actually download a disk image, or a virtual image of a removable disk. They have the extension “.dmg” minus the quotation marks.

When you double-click the disk image file, the disk image mounts to your desktop and it opens, revealing the Firefox (or whatever application you downloaded) icon. I bet you’re just dragging that icon into your dock and running it instead of dragging it into your Applications folder first.

So do that, drag the application’s icon into your Applications folder first, then drag that icon into the Dock, eject the disk image, and your disappearing act should be a thing of the past.

Thanks for writing in, Charles, and anyone else is invited to send me your questions and I will do my best to put together a tutorial for you. All throughout the month I answer more questions and post other useful Macintosh and iPhone related articles on the website, so go over to boropulse.com and look in the Scoop section for my stuff!