Visual Diff
Good Examples
https://www.google.com/docs/about/
OK examples
http://text-compare.com/
https://www.diffchecker.com/diff
Terrible Examples
http://www.textdiff.com/
http://codebeautify.org/file-diff
The Visual diff visualization is a visualization usd for comparing two texts quickly to see where the differences in the texts appear. It seems to be used mostly for finding differences in two blocks of code quickly. Already, the way that these systems are already set up to be pretty standardized. The original text shows changes on the left highlighted in green while the changed document shows the discrepancies highlighted in red. That being said not all visualizers are created equal.
I find that the bad examples say far more about what makes this visualization system successful. At http://www.textdiff.com/ the visualization returns a set of strings that tell you where the differences are, and arguably is not even a visualization at all. At http://codebeautify.org/file-diff, the website simply returns a bar graph that shows the indices of where text has been deleted, changed or simply does not show up and then returns the original text and the changed text with no visualization of where the changes have been made.