1. Start Any HL1 mod
2. Developer 1 in console
3. Find a server with custom content and fast download
4. Press cancel just after the fast download begins
5. Look in the console for the url
6. when the url for example is:
http://123.123.123.123/cstrike/maps/custommap.bsp
change the url to http://123.123.123.123/cstrike/server.cfg and open it.
And you might be lucky.