Why does Microsoft Edge (formerly Project Spartan) prompt to open this website in Internet Explorer?

Question

Does anyone know what triggers MS Edge to not open a specific web page/site, but instead prompt the user to open the site in internet explorer?

The message says:

Answer 1

You can do the sitescan on http://dev.modern.ie/tools/staticscan/ to get some hints on why the site might not render correctly in MS Edge. Like Charles already said the behavoir itself is controlled by the compatiblity list. Check out this blog post for a list of older technologies that are not supported in MS Edge: http://blogs.windows.com/msedgedev/2015/05/06/a-break-from-the-past-part-2-saying-goodbye-to-activex-vbscript-attachevent/