Added instructions on setting the proxy host.

Mac/OSXResources/app/Resources/English.lproj/Documentation/packman.html

@@ -50,6 +50,12 @@
 				with the <tt>File-&gt;Open URL...</tt> command, but you should realize that
 				you are now on untested ground.</p>
 				
+				<p>Another potential problem source is that you are behind a firewall. This version
+				of PackageManager uses the Unix method of setting a firewall: you need to set the
+				environment variable <tt>http_proxy</tt> to <tt>"http://<i>proxyhost</i>:<i>port</i>"</tt>.
+				See <a href="http://developer.apple.com/qa/qa2001/qa1067.html">Apple Technical
+				Q&amp;A QA1067</a> for instructions.</p>
+				
 			</td>
 		</tr>
 		</table>