Attack signature page is blank

I have been received regular alerts saying that I am being attacked by Portscan.

When I choose to learn more about the attack, I receive a link:

 

http://www.symantec.com/security_response/attacksignatures/detail.jsp?asid=99991

 

But when I navigate to that page, the page is blank.

i would like more information about this particular attack signature, but I don't seem to be able to do that here. 

Please advise.

 

Thank you.

 

 /gh