At the moment there is no undo feature in the LiveEditor.
If you make changes whilst editing a page in the LiveEditor and have not clicked “save and continue” or reloaded the page for any reason, you may be able to abandon your changes by closing the page without saving (click the X in the top right corner of the page).
In recent versions of OptimizePress we have also added a “revisions” feature which you can access from within the LiveEditor to go back to recent autosaved versions of your pages. Our system auto-saves your pages every 5 minutes