STEP 1. Simply launch the Terminal.
STEP 2. Now replace the URL of the website you like to mirror locally using the following command:
wget -m http://www.guimp.com/
In the above case www.guimp.com is the URL of the website. You can replace it with the URL of the website you wish to mirror locally.
That’s it. Now the entire website will be downloaded on your local drive of your Mac OS X in a directory named the websites URL. In this way you can mirror a complete website locally on your Mac OS X. You should note that this is not an effective way to backup a website, and it’s functionality. [Via]