Have tried several suggestions found in the support community, some suggesting to delete a preferences file which I cannot find. I have iMacs at work and at home., but I am having this problem only on one of the Macs.
iMac, Mac OS X (10.7.2)
So you've tried clicking on the icon > Options > Keep in Dock?
The reason you can't find the preference is because the User Library is hidden.
Go to your Finder "Go" menu hold the option key to choose "Library". Then go to Preferences/com.apple.dock.plist and delete that file. Log out and back in or restart.
This will reset your Dock to default so you'll need to set it up the way you like it, but if there's any corruption it should remove it.
So you've tried clicking on the icon > Options > Keep in Dock?
The reason you can't find the preference is because the User Library is hidden.
Go to your Finder "Go" menu hold the option key to choose "Library". Then go to Preferences/com.apple.dock.plist and delete that file. Log out and back in or restart.
This will reset your Dock to default so you'll need to set it up the way you like it, but if there's any corruption it should remove it.
Back up all data.
In the Finder, hold down the option key and select
Go ▹ Library
from the menu bar. From the Library folder, move the following items to the Trash, if they exist:
and move the following items to the Desktop:
Here “*” stands for a long string of letters and numbers.
Next, triple-click anywhere in the line below on this page to select it:
open $TMPDIR../C
Copy the selected text to the Clipboard by pressing the key combination command-C.
Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the page that opens.
Paste into the Terminal window by pressing the key combination command-V. A folder should open. Inside it there may be a file named "com.apple.dock.iconcache". If there is, drag it to the Trash.
Log out, log back in, and test. If you still have the issue, put the items on the Desktop back where they came from and post again. Otherwise, delete the items.
on restart why do all app icons in the dock, except Apple apps, disappear? OS X (10.8.5)
