To compare or just to watch the site as it is, it might be practical to have a Leave version tag (or "Go back to the Live page" or whatever) function. Now it can only be done by or changing to another version tag or to log out and refresh a couple of times (for end-users this is confusing).

Also, you don't want to set your cache timeout to a very small interval, then your server gets a unnecesary high load. (of course you can set it back again, but forgetting is human)

While making some more rigorous changes I often want to do this, but it takes a while. Also, not everybody has two computers so they can have the two next to each other.

This probably should include an automated "Clear Cache" function and a reload of the page. 

Bart