generates proper HTML for respective browser from downlevel and up.
The only problem you may encounter if you use older .NET Framework
(below version 4.5 which is current at the time of this answer) with the
latest browsers (such as IE10, IE11 - latest at the time of this answer).
Then it may not recognize the browser and generate incorrect
Otherwise non MS-browsers have no problem accessing and vieweing ASP.NET
P.S. Of course you can encounter problems if you write IE-specific