Use the command line, as described in this related question: How do I check if my SSL Certificate is SHA1 or SHA2 on the commandline.
Here's the command. Replace www.yoursite.com:443
to fit your needs. Default SSL port is 443:
openssl s_client -connect www.yoursite.com:443 < /dev/null 2>/dev/null \
| openssl x509 -text -in /dev/stdin | grep "Signature Algorithm"
This should return something like this for the sha1:
Signature Algorithm: sha1WithRSAEncryption
or this for the newer version:
Signature Algorithm: sha256WithRSAEncryption
The article Why Google is Hurrying the Web to Kill SHA-1 describes exactly what you would expect and has a pretty graphic, too.