See "Reset Download Actions"

• http://kb.mozillazine.org/File_types_and_download_actions

• https://support.mozilla.com/kb/Managing+file+types

9/28/11: Spoke too soon. Deleted the file in finder "mimeTypes.rdf" as indicated. However, once I go back to Firefox (and I don't know which website, if that is the issue), the box comes back again.

Unable to do "Resetting Download Actions" because the things they request to do in step 2 and 3 are not there:

Resetting download actions

This applies to all versions of Firefox and Mozilla Suite/SeaMonkey

If problems arise or if you want to restore the default set of file download actions, do the following [8]:

   Type about:config into the address bar.
   Find the preference browser.download.pluginOverrideTypes and, if it is present, right-click on it and select reset.
   Find the preference plugin.disable_full_page_plugin_for_types and, if it is present, right-click on it and select reset.
   Open the profile folder. (The profile folder is hidden by default in Windows 7/Vista/XP/2000 and Linux; read this for help finding it).
   Note: In Firefox 3.6 and above you can open the profile folder from the Firefox menu, via "Help -> Troubleshooting Information".
   Completely close your Mozilla browser.
   Delete (or rename) the file mimeTypes.rdf. Caution: There is also a mimeTypes.rdf file in the program folder. Do not delete it by mistake.

Thoughts?

9/27/11: Thank You very much for your reply. Working and trying stuff from both links, I eventually got it resolved...so far.

thx

Clear the cache and the cookies from sites that cause problems.

"Clear the Cache":

• Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"

"Remove Cookies" from sites causing problems:

• Tools > Options > Privacy > Cookies: "Show Cookies"

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.com/kb/Safe+Mode

• https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes

Do a malware check with some malware scanning programs.
You need to scan with all programs because each program detects different malware.
Make sure that you update each program to get the latest version of their databases before doing a scan.

• http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware
• http://www.superantispyware.com/ - SuperAntispyware
• http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page
• http://www.safer-networking.org/en/index.html - Spybot Search & Destroy
• http://www.lavasoft.com/products/ad_aware_free.php - Ad-Aware Free

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

I should have indicated before. I have the new Macbook Pro. Is all that malware scanning necessary?

thx

No, sorry that doesn't apply to Mac Those programs are for Windows only.

Are you using any programs that handle PHP files and that may have set an action system wide?

Does that pop-up mention any MIME type in the dialog window?

1. I don't know and I don't know what PHP files are or what programs would use that.

2. No, the pop-up does not mention any MIME in the dialog window.

Interestingly (and I have not had a chance to perform the new tasks you have sent yet), after I delete the "Mimetypes.rdf" file in the profiles and then re-open Firefox, the pop-up shows up, but not sure if it is just Firefox in general or if it is the re-opening of a particular website that I "always" have open. I'll have to try to figure that out as well.

If it says Plain text like you posted above then that implicates that the file is send as text/plain and that should force Firefox to display the file as text in a browser tab.
That is of course still not what you want as such files need to be send and received as text/html.

Do you have any security software that may have changed the HTTP response headers?

Cor-el,

sorry been M.I.A. for a few days.

"Do you have any security software that may have changed the HTTP response headers? "

No, I don't think so.