User Agent String.Com 

User Agent String explained :

Mozilla 1.2.1
Mozilla	Name : Mozilla
5.0	Mozilla version
X11	X Window System a windowing system for bitmap displays
U	Security values: N for no security U for strong security I for weak security
FreeBSD i386	Operating System: FreeBSD running on a Intel 80386 CPU
en-US	Language Tag, indicates the language for which the client had been localized (e.g. menus and buttons in the user interface) en-US = English - United States
rv:1.2.1	CVS Branch Tag The version of Gecko being used in the browser For the Mozilla browser this is the browser version as well
Gecko	Gecko engine inside
20030202	Build Date: the date the browser was built
Last visit:	2018.07.29 06:14
All Mozilla user agent strings