Xorg Version numbers

[fossks at cox.net]

I apologize for asking such as basic question but could someone clarify the version numbering system used within Xorg.

I've been the Xorg website where it states that 7.3 is the current version.  I've ran across a number of sites where they are using numbers now like 1.4.2, 1.4.0.90, 1.3, etc.   It doesn't seem to match.

And when I thought it couldn't get more confusing, I found xorg input driver modules like evo_drv.so that give errors when they are used because they were compiled against 4.3.99 when the driver vendor states they support Xorg versions 7.2 and earlier.

Major sites like Distrowatch use all of these numbers so I would really like to get it cleared up from the people who should know.

Thanks.