Hi there...when you are using the Safari browser, there is a back button in the upper left corner to go to the page last visted.
For a substitute for an "escape" button...you can press your home button to return to your home page. Or, if your iPad is updated to 5.0 or greater, you can also "escape" by doing a 5-finger pinch to exit out of the app and back to the home page as also.
When typing something, to go back to a word, jut press on the word until the magnifying glass pops up. From there you can edit the word or delete as needed.