Does anyone know if a wildcard certificate is supported across all browsers: IE6, IE7, IE8, Firefox, Chrome and Safari? If I were to access the following secured sites sharing one wildcard certificate across all browsers, I won't be prompted by the browser:
https://one.example.com
https://two.example.com
https://three.example.com
The three addresses you listed there will work with a certificate for *.example.com. Be careful with other names you might add in the future if they have more words separated by periods. The meaning of * for certificates is inconsistent between browsers. Some will match anything, others will match only one word separated by periods.
The cert usually isn't the problem, but the issuing CA. Nowadays any major SSL provider is going to be compatible with 99% of browsers.
Yes, they will work in all browsers as long as you configure them properly.