How can I check if a server has ssl enable or not

You don't specify a programming language, but you could do this from the command-line.

bash-3.2$ echo ^D | telnet www.google.com https
Trying 66.102.11.104...
Connected to www.l.google.com.
Escape character is '^]'.
Connection closed by foreign host.
bash-3.2$ echo ^D | telnet www.stackoverflow.com https
Trying 69.59.196.211...
telnet: connect to address 69.59.196.211: Connection refused
telnet: Unable to connect to remote host

There you go... Google does, StackOverflow does not.

"It's easier to ask forgiveness than permission"

For example, to read stackoverflow.com via SSL, don't ask whether stackoverflow.com supports it, just do it. In Python:

>>> import urllib2
>>> urllib2.urlopen('https://stackoverflow.com')
Traceback (most recent call last):
...
urllib2.URLError: <urlopen error (10060, 'Operation timed out')>
>>> html = urllib2.urlopen('http://stackoverflow.com').read()
>>> len(html)
146271
>>> 

It shows that stackoverflow.com doesn't support SSL (2008).

---

Update: stackoverflow.com supports https now.