I found solution to my problem by doing this:
1-assured that in /etc/papersize there is written only a4.
2-open /usr/share/ghostscript/8.71/lib/ghostpdf.ppd and erase every line with inside the word "letter".
3-open /etc/cups/ppd/KM-1635.ppd (instead of KM-1635 use the name of the printer that doesn't print to a4) and delete the line where there's write letter/letter like this
4)changed in firefox at about:config every line where there's letter on na_letter or letter to a4 and the dimension of that format forced to height 297 and width 210. when i restart firefox the values of print.postscript.paper_size was returned to letter for example but the printer print correctly to a4.
I found solution to my problem by doing this: ghostscript/ 8.71/lib/ ghostpdf. ppd and erase every line with inside the word "letter". ppd/KM- 1635.ppd (instead of KM-1635 use the name of the printer that doesn't print to a4) and delete the line where there's write letter/letter like this
1-assured that in /etc/papersize there is written only a4.
2-open /usr/share/
3-open /etc/cups/
*PageSize Letter/Letter: "%% FoomaticRIPOpti onSetting: PageSize=Letter" ionSetting PageSize=Letter: "-p1 "
*FoomaticRIPOpt
*PageRegion Letter/Letter: "%% FoomaticRIPOpti onSetting: PageSize=Letter"
*ImageableArea Letter/Letter: "12.00 12.00 600.00 780.00"
*PaperDimension Letter/Letter: "612 792"
4)changed in firefox at about:config every line where there's letter on na_letter or letter to a4 and the dimension of that format forced to height 297 and width 210. when i restart firefox the values of print.postscrip t.paper_ size was returned to letter for example but the printer print correctly to a4.
Sorry for my english... Bye