I'm presently on the mac while using pre-installed Apache server.

Now I have to mix-browser test some websites, and for that reason I have to access my pages on another computer systems. How do i make my localhost-sites accessible for other computer systems on my small Wi-fi compatability (without uploading to a different server)?

Thanks ahead of time.

Apache server's default configuration should allow other computer systems (even ones this is not on the local network) to gain access to whatever it's serving up.

You have access to your server from another machine using the Ip of the server. You'll find the Ip of the server by getting a console (this works in Home windows and Mac machines) and typing in "ipconfig". (For linux machines, it's "ifconfig".)