Help! Strange message when trying to pay for item...

[st311ar]

I bought some cufflinks from aussietiesonline, however when I click on Pay Now I get this message: "

	There is a problem with this website's security certificate.
	The security certificate presented by this website has expired or is not yet valid. Security certificate problems may indicate an attempt to fool you or intercept any data you send to the server.
	We recommend that you close this webpage and do not continue to this website." What does this mean? What should I do? Thanks.

[robert9422]

I got this message yesterday when I tried to pay for something when I was at my home computer, "The site's security certificate is not trusted!" so I backed out of it.  I also got the same message today when I tried to pay from my work computer.  Never seen this message before.  Apparently the certificate is expired.  When is this going to be fixed?