There are several ways:
1) Edit your /etc/hosts.txt file and add a line for "127.0.0.1 www.google.com". (That file is in system32, I think for windows) Don't forget to remove that entry when you're done.
2) Do a search-and-replace on the files while editing. Something like perl -i.bak -pe 's/www.google.com/localhost/' *.html
would work.
3) Use a proxy that can modify data. https://github.com/evaryont/mousehole
4) Use greasemonkey or similar to modify the page via javascript.