It is not enough to simply change the User-Agent string to Googlebot if the website in question checks for cookies, uses Javascript for detection or compares the IP to make sure it is indeed in Google’s IP range. Using just the User-Agent might work to gain access into some websites but others probably will not work because they perform additional checks.

Here are the five factors that are important:

• IP: Use Google Translate to surf the site
• User-Agent: Use the Firefox Extension User-Agent Switcher and add the information about Googlebot.
• Javascript: Use a Firefox Extension like No Script to turn it off.
• Cookies: Use the Firefox Extension Cookie Safe to block cookies that the site tries to set.
• Referrer: Use the Firefox Extension RefControl to disable the Referrer.

The website describing the techniques is currently down because it was not able to handle the massive amount of visitors that Digg and other sites sent to it.