SSO and SSL Certificates

I was ask to use a different SSL certificate for my SSO 开发者_如何学运维web service and a different SSL certificate for my website.

Why would I need a different SSL certificate when both the website and webservice are under the same IIS?

Usually certificates are issued to a particular domain. If your website and webservice are on different sub domains then you would use a different certificate for each. Alternatively you can obtain wildcarded certificates (ie. *.yourdomain.com) but these tend to be much more expensive.