I have been looking for a while for a good open source program/plugin such as this and I have to say this is very helpful and worked without flashing or moving around so it was easy to see the change that was made even if it was very slight.

One issue I came across when using this was that I wasn't able to zoom in. Normally when using IE the user is able to zoom in using CTRL +. This is very useful when designing a HTML page so that things can be examined closely and moved slightly to line up. Being able to zoom in would be a very helpful feature.

Ctrl+/- doesn't work, that's true; I may add it some day.
But in the mean time, you can still zoom in and out using Ctrl+MouseWheel, just like in the browser.