https://support.mozilla.org/en-US/kb/how-print-websites#w_format-and-options

Select Portrait in Page Setup Options.

The Web-page I want to print is above then 1 page width. It is 5 inches (15 sm) height and about 50 inches (1,5 metres) width. Or the same sizes...

Its like Gantt chart, where the width is more important when height.

Is it difficult to develop this type of page printing?

OK, now I understand what you want to do.

Probably not difficult per se, but that really isn't a Firefox issue. Paper size selection isn't done in Firefox, but rather that is selected in the printer software. Mozilla calls that the "native print dialog" box.
It's more an issue of having or finding a printer that supports custom paper sizes like you are referring to. Definitely not a "consumer" type printer, unless you are talking about pin-feed continuous sheet printers that were popular in the consumer market-place in the 80's and 90's. Typically ribbon-type "impact" printers that used folded paper which fed out of a box on the floor or on the lower level of a rack the printer sits on.

Is your need for something like this a one-time thing, or something you would need to do frequently?
Around here I would save a chart like that as an image, to a USB Stick, and take to either Staples or FedEx Office; or email them the file, have them do their thing and call me when it was ready.

I'm glad you understand me and spend you time. There are much people want to use this "feature". I add an image of MS Excel (3 horizontal sheets printing on the page size 297 mm x 210 mm - A4) and our company (users of FF) want FF to provide this feature.

If you want to see a part of example, you can go to http://palayner.com/construction/geo/_14 all you need login "17736" and password "qwe" (without quotes, of course). You will see a long chart in 2 dimensions: kilometres and worktypes. How to print it? May be, it's better teach FF to rotate such pages or print it on several A4 (A3, so on) sheets, like MS Excel do?

Shall we hope you develop this?

Thank you very much for spending you time, mr. The-edmeister

File a Bug report under RFE (Request for Enhancement), which is the first step for new feature consideration.
https://bugzilla.mozilla.org/

https://developer.mozilla.org/en/Bug_writing_guidelines

Or dialog box like this: First print top left page, than left pages one by one, then top right page, and so on... (russian language at the picture)

-> File a Bug report.

It was so difficult for me to explain what I want to you using Englich, I think other people will not understand me ((

As in your screenshot of today - Mozilla / Firefox doesn't generate that printer preferences box, it uses what is available in the operating system as supplied with the printer software. If you're not seeing that preference in the dialog available thru the Properties button in Firefox, it isn't a feature of that printer in Firefox.

The best I can offer is to save that "page" as an image (screenshot), turn it sideways in a graphics program so it's tall and narrow, and print it sideways.

Either that or save that page to a USB stick and take it to someone who has a plotter type printer (extra wide paper on a roll). Over here we can get that service from Staples and FedEx Office stores.

Today I have rotate the horizontal page to vertical, using css property "transform: rotate(90deg);"

http://palayner.com/construction/geo/_14print

login "1111" password "qwe" (without quotes)

I see that vertical pages Mozilla FF can't print. What is interesting, Google chrome can. It's terrible!

I don't want leave FF browser and go to use chrome, becasuse there are many problems with chrome (table display, ajax-queries and so on). I wanna see correct page printing in FF!

No need to "leave" Firefox for a different browser. You can have both installed, and use both browsers - even at the same time.

As far as "correct" page printing goes, who is the arbiter of what is "correct"?

FF displays for print only one page. Chrome displays several pages, as they realy are. That's why I said "correct". I hope, FF will have this "clever" page print setup/display as Chrome has.

->You can have both installed, and use both browsers - even at the same time

I shall follow your advice. It is a good compromise

I would also like the ability to print large posters via Firefox.

So I was about to request the above in addition to the below since I need both features:

The ability to print multiple copies of identical-images per page, sorta like the Windows photo wizard, except better. After I got disgusted with the non-flexibility of Win-Wizard in my now-ancient XP, the reason I imported my image to Firefox, was due to FF flexibility at adjusting margins via page-setup. But then I realized that FF doesn't offer duplicating of the same image several times per page.