Oops, I'm sorry, but your Browser is not capable of showing multilingual URL's correctly
In other words, your browser is not W3C compliant with respect to URL rendering and will instead show the PUNYCODE equivalent rather than the multilingual Unicode characters as it should. As a result, your browser was directed to this page, which shows the standard ASCII sigma-domain.com instead of ∑.com. You see, PUNYCODE was never intended by the IDNS WG to be seen by the end-user but some browsers just haven't caught up with the current technology.
If you want to see this URL properly, then do one of the following:
If you're running Windows:
There are plug-ins that will allow IE to support IDNS here.
If you're running Macintosh:
Then switch to the Safari Browser.
In any event, you'll need to use one of the above Browsers, or plug-in's, to see this url demonstration.
To read more on IDN's, please review here.