limitations of .aspx web pages rendered in OS X Safari Specifically, 

The goal is to understand the degree of compatibility of Safari with .aspx services.  Is there a comprehensive list of .aspx functionality that fails in Safari? OR 

Is there a method \ line of thought to evaluate an .aspx page to determine any functional limits from a Safari perspective?

Although one can simply try the pages in Safari, I am reluctant to try it with this government website:

https://ritx-fl-sut.bswa.net/ 

State of Florida Department of Revenue website for reporting sales tax. The website allows me to login with Safari, but indicates:


  This website is optimized for use on a PC using Microsoft Internet
  Explorer. If you are using any other web browsers, this site may not
  appear or function as designed. We do not officially support the
  Macintosh platform.
ASPX is a Server Side Choice

ASPX is a server side technology. The web pages created by ASPX are not inherently limited on Safari browsers.

This is the same for other server side technologies such as Java, php, and perl.

Developer's Responsibility

The developer of the .aspx created page is responsible for producing content that conforms to widely accepted web standards. These standards include HTML5 and those published by the World Wide Web Consortium.

Web developers can refer to resources such as QuirksMode for a guide to what features are supported by which browsers.

Webmasters' Stack Exchange

For help with specific web technologies and choices, please ask on the specialised Webmasters Stack Exchange.