See this:
http://kb.mozillazine.org/Problems_printing_web_pages

I went to the webside you directed me to but was unable to find there anything that would even relate, leave alone help solve my problem.

Could we please try again?

My problem is that:

When I try to print to the HP PSC 750 inkjet printer, a "Printing" dialog box appears, showing Title: xyz and a progress meter showing 100% but this is being overlaid almost immediately by a second dialog box stating "An unknown error occurred while printing" and, while the printer continues saying "printing", no printing will take place.

And, by the same token:

When trying to print to the Brother HL-5240 laser printer, printing will occur but all formatting is lost and what comes out is a block of unintelligible running text.

What can/must I do to get Firefox to print correctly to my two printers?

I would very much appreciate if I could hear from you once more on this. Thanks :-)

Did you try doing the Reset mentioned on that page, for the HP?

As far as the Brother, see what the Default font is set to in Options.
Tools > Options > Content = Fonts & Colors
Is that set the Times New Roman ??

Yes, I did the reset but it made no difference. However, in parenthesis there is that note that reads''"Some users may need to reset all the print_printer preferences for a particular printer, if resetting this one master preference doesn't solve the problem".''

Would that mean resetting all of the 37 line items that pertain to Brother HL 5240?

Would it _also_ pertain to all of the 68 line items that pertain to HP PSC 700, my second printer?

And what about the two printers showing that have been discarded several years ago: 37 line items for Brother MFC Pro printer and 30 line items for Okidata OL 600e. Is there a safe way to delete all of them?

If there is, how would I go about that? When I right click on any of these line entries, the options that become available are, as it appears, for modifications only, not for deletions. They are Modify: Copy - Copy Name - Copy Value - New (String-Integer-Boolean) - Reset.

Lastly, with respect to the Default font, it was set to Verdana, my font of preference. Still, I have changed that to Times New Roman, since it sounds as if that is what you would like to see there.

What seemed odd was that the font size showed as having been set to 16 which I never use - and I reset that now to 12. I assume that this is what it should have been set to in the first place. Is that correct?

Please stay with me!

1. Right-click and Reset every preference for the HP printer that is giving you that "unknown error" message. Resetting only the main pref seemed to work for most users a few years ago when myself and others over at MozillaZine started working up a list "fixes" for printing issues and that Problems_printing_web_pages article was written, but users started reporting that they had to clear all the prefs to fix things - so that recommendation was added.

An easier way of clearing all those prefs is to edit them out of the prefs.js file using a simple text editor (with Firefox closed). You can highlight all the lines all at once (they're all listed together) and then hit the Delete key, but you can't screw up the one-line per pref formatting or you break everything beyond the screw-up. Make a backup of that file before editing it in case you screw up the formatting and your prefs disappear.
http://support.mozilla.com/en-us/kb/Profiles#How_to_find_your_profile

2. Times New Roman & 16 are the default settings you should try, but I'm not sure that is going to fix that problem. There is a Bug related to "font glyphs" that is causing that problem with some print drivers. I have a very minor occurrence of that unintelligible text on some headings with my Brother HL-2070N laser jet, which I haven't been able to cure. Fortunately that unintelligible text shows up in Print Preview, so when I see it I just switch to using my Brother MFC-J615W inkjet whose print drivers don't seem to be affected. I Preview everything I want to print to see what it will look like and not waste paper & ink/toner.

There are some fixes for printing coming in Firefox 4, but I'm sure if these two problems are fixed or not.

Cleared all the prefs for my two printers, Brother HL 5240 and HP PSC 700 (actually PSC 750). To my greatest surprise, the line item print.print_printer on which I entered RESET yesterday is no longer showing in the list. What can have happened to it? Can I live without it?

Following that, attempted printing from web pages and it worked fine with both printers.

Then, I downloaded and installed an add-on that Firefox offered. Went to Paypal for a donation and wanted to print that page, using my HP PSC 750 which, as I thought, would perform correctly now. Not so, it again displayed the PRINTING dialog but nothing happened. Just as before.

The Brother HP-5240 printer continued printing correctly.

I really don't know what to make of this.

In addition, and not directly related, I can not find the downloaded add-on anywhere. Don't know where Firefox stores these add-ons nor how I can access/configure/make use of them.

It seems that you did not comment with respect to my question about clearing/removing from about:config the actual line items that refer to the two printers I have not owned for years. Should I remove those and if so, how would I do that? Delete every line item in the list that refers to them?

Surprise!

When going back to about:config This morning, the line item print.print_printer that went missing yesterday has re-appeared all safe and sound.

Pleasing, but weird, if you don't mind my saying so :-)

1. print.print_printer will reappear after you print something. That pref is the last used printer, so when you reset that pref it doesn't appear until you print something.

2. Being that your problem with the HP printer reappeared so quickly, try a new Profile.
http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows

3. Regarding the prefs for the old printers, if you reset those prefs they won't come back (assuming you don't accidentally select those printers or the printer drivers are uninstalled).

My Brother HL-7050 Laser prints garbage when printing off net or emails....Brother said to call Mozilla and get a print driver/DLL from them. Haven't done that yet. Just checking this site.

@tropicalbecki,

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