Explanation

When using the "back" button to return to a form with elements that were disabled via javascript, those disabled elements are no longer disabled. The opposite is also true; fields enabled via javascript are no longer enabled when going back.

Other field attributes such as value and checked are not affected in this way.

Demonstration

Use the buttons to disable/enable the fields and submit them, and then look at their state when you return to this page.

Fields enabled by default
Fields disabled by default