Most popular variants of the header value (we only show this when there's just a bunch of variants):

• 4.0.30128
• XXXXXXXXXX
• WebServer
• 4.x.x
• -
• 4.0.30319, 20.0
• 1.1.4322
• 791423640900000001
• None
• 10.0.0
• ASP.NET
• 4.0.30319, " "
• 0
• 2.0
• FF5C4086932D5FB80A7603AB1AC684AD2CC810CF6F15936DC…
• 4.0.30319, PHP
• 4.0.30319
• 0.0
• "5.5.50728"
• N/A
• 2.0.50727, 2.0.50727
• PHP
• Bimsa
• PAX Version
• XXXXXXXXX
• 2.0.50727, UnKnown;
• 791423640900000000
• DENY
• Custom
• 9.4.5.3
• s
• DFM 1.0
• A web framework version
• 1.21.366
• " "
• 2.0.50727
• Ravian
• 791423640900000002
• 4.0.21006
• v1.1.1
• XXXXXXXX

A non-standard header used by Microsoft ASP.NET platform to advertise its detailed version.

Reference...