Enable revisions by default for all content types

Revisions should be enabled by default so that historical versions are preserved, which allows administrators to easily restore a previous version or else simply confirm what information was displayed at a certain point in the past. Revisions are how you "undo" content changes in Drupal.

1. Go to Administer->Content management->Content types (.../admin/content/types)
2. Enable revisions by default for the Page content type
   1. Click the edit link for Page
   2. Click on Workflow settings to expand that section
   3. Enable (check) Create new revision
   4. Click the Save content type button
3. Repeat for the Story content type:
   
   1. Click the edit link for "Story"
   2. Click on Workflow settings to expand that section
   3. Enable (check) Create new revision
   4. Click the Save content type button
4. Whenever you add or create a new content type (such as when enabling the book module or creating a custom content type), enable Create new revision by default for that content type.