Wiki keeps track of histories of changes on a page by maintaining a version of the page each time it is modified. To compare two versions, select two checkboxes corresponding to each relevant version, then click 
.
A page which shows the changes between these two versions will be displayed.
The changes between two versions will be marked with colors:
Words/lines which are red-highlighted with strike-throughs indicate that they were removed.
Words/lines highlighted in green indicate that they were added.
Note
Only two revisions can be selected at one time.