Unfortunately, AFAIK, this setting does not exist. (It doesn't exist in another WebKit browser, either: Google Chrome. You can do this in Firefox, though, using 'about:config'.)
About hard-coded cipher priorities/support for the SSL/TLS handshake:
I tested that Safari does not support 40-bit RC4 encryption with an MD5 hash. This means that it does not support some products that are required by US export law to use low (<64-bit) encryption.
See also:
http://www.carbonwind.net/blog/post/A-quick-look-over-some-browsers-and-their-SSLTLS-implementations.aspx
"Initially, in SSL/TLS negotiations, TLS with RSA and weak 128-bit RC4 keys are offered first and second in the cipher order. Worse, ECC (Elliptical Curve Cryptography), AES (Advanced Encryption Standard), and 256-bit keys are never offered as potential cipher choices; further, MD5 is offered first and more frequently than SHA-1, when it should be the other way around."
By Roger A. Grimes, Infoworld Feb 1, 2009 1:19 pm
http://www.pcworld.com/article/158706/how_secure_is_safari.html
Recent versions of Safari do not appear to display the lock icon or certificate unless all content loaded by the page is https. For example, if the page URL is https but it loads a JavaScript file via http, no lock icon.
The only workaround I've found so far is to run the openssl command in Terminal, like this:
echo ^d | openssl s_client -connect host.example.com:443
This will show you the certificate chain back to whatever root authority is used to sign, if any. "verify error" will show things like "self signed certificate".
Best Answer
Yes, it is possible.
YMMV depending on which app you're using or which SSL/TLS library you're using, if you're talking about your own app.