Windows error opening Internet shortcut or local HTML file - Firefox

On some Windows systems, if Firefox is not already running and you click an Internet shortcut or local HTML file, two instances of Firefox may open, or Firefox may open along with the error dialog,
"Windows cannot find <url or path to file>. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search."

Also, if Firefox is not open and you click a webpage link in a document or spreadsheet, Firefox may open a window with a message that the page could not be found with the address bar showing "FirefoxHTML%5CShell%5COpen%5CCommand" appended to the URL. [1]

An installed extension can cause the error dialog, specifically Adblock Plus version 0.7.5.2 [2] (fixed in version 0.7.5.3) so you should update your extensions as a first step. If the problem continues, try the following solutions (you may need to repeat these steps after a Firefox update):

File Types edit

(In Windows XP and Windows 2000)

1. Open Windows Explorer (or My Computer).
2. Go to Tools -> Folder Options -> File Types
3. Select Extension: "(NONE)" File Type: "URL:HyperText Transfer Protocol"
4. Click "Advanced". In the "Edit File Type" window, select "open" and click "Edit"
5. Uncheck "Use DDE" (the dialog should then hide the lower part).
6. Click OK for that dialog and the next one (afterwards, the "Use DDE" box is still checked but the "DDE Message" box will be cleared, as shown here)
7. Repeat for Extension: "(NONE)" File Type: "URL:HyperText Transfer Protocol with Privacy" (and any other protocols you want to fix)
8. Repeat for Extension: "(NONE)" File Type: "Firefox URL"
9. Repeat for Extension: "HTM" (or "HTML") File Type: "Firefox Document"

Sources:

• Bug 246078 comment 6
• Bug 367899 comment 5
• MozillaZine forum post (more here and here)

Note that the "File Types" user interface as described above is not available in Windows Vista [3] so you will need to edit the registry.

Registry edit

You will need to manually edit the registry in Windows Vista or in cases where the File Types listing is missing certain entries such as "URL:HyperText Transfer Protocol" (HTTP) and "URL:HyperText Transfer Protocol with Privacy" (HTTPS).

Caution: Editing the registry incorrectly can damage your system. Do not attempt these steps if you are inexperienced or uncomfortable using the Registry Editor.

1. Go to "Start -> Run" (or press the windows key+R) then type regedit and click OK
2. Use the directory tree hierarchy to navigate to "HKEY_CLASSES_ROOT\HTTP\shell\open\ddeexec"
3. Delete the "ddeexec" registry key
4. Repeat for "HKEY_CLASSES_ROOT\HTTPS\shell\open\ddeexec" (and any other protocols you want to fix)
5. Repeat for "HKEY_CLASSES_ROOT\FirefoxURL\shell\open\ddeexec"
6. Repeat for "HKEY_CLASSES_ROOT\FirefoxHTML\shell\open\ddeexec"

Sources:

• Bug 137363 comment 9
• Bug 372016 comment 7
• MozillaZine forum post

Related bug reports

• Bug 246078 (2windows) – URLs from other apps result in two Firefox windows or a window and an error dialog (Set as Default Browser does a lousy job creating ddeexec keys)
• Bug 353089 – Fix / remove ddeexec hack
• Bug 359630 – Windows cannot find 'SHORTCUT' when clicking link from desktop after crash
• Bug 367899 – FirefoxHTML%5CShell%5COpen%5CCommand is added to URLs linked to from another application
• Bug 370053 – Clicking a URL shortcut icon opens two instances of Firefox
• Bug 389502 – [meta] "Windows cannot find .... Make sure you typed the name correctly, and then try again."