This script supports Netscape 3.x and 4.x, as well as Internet Explorer 3.x and 4.x. However, there are still a couple of quirks under Netscape 4.x, mainly relating to window resizing. You can try the simpler Java version here if you aren't happy with the output.
To print the generated calendar, use your browser's Print command. For printing, you may like to check the "Display full calendar in 3x4 format" option -- it would save you some paper. Or, to paste it into any HTML-aware application (most word-processors and email clients these days), highlight the calendar, then choose your clipboard Copy command.
This created a calendar without any accuracy problems upto about 33000CE (Common Era, the new politically correct term for AD). However, the Gregorian calendar was initially adopted only in Catholic European countries. So don't expect very early dates generated by this program to match those in national calendars of many countries -- notably Russia (upto 1919) and Britain (upto September 1752). Here is a readable brief history of the development of the Gregorian calendar.
While on Britain, look at what my Linux cal program generates... a decidedly Anglo-centric view of the world, in my opinion.
cs96a2205@linux5 ~$ cal 9 1752 September 1752 Su Mo Tu We Th Fr Sa 1 2 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Rendering of the generated HTML under Netscape 3.x and IE 3.x has been fixed, but I can't say anything about Netscape 2.x or IE2. Heck, I don't even know where I can get my hands on those antiques!
The 25000 year limit is there for a reason -- many 16-bit machines overflow for larger years. The Gregorian calendar itself requires corrections after 33000CE or so, so you aren't missing much.