Follow-up: One of my colleagues is working on a product feature that involves checkboxes (this is how I came across this issue in the first place). His checkboxes aren't contained within a form element whereas in my test page I described in my question when I removed the form from the page the issue didn't manifest. However, the page he's working on does contain other forms so I decided to modify my test page to try to replicate this scenario. I found some really odd behavior. If I have a form on a page but the checkboxes are not children of that form, and if I dynamically add a single INPUT element or a single TEXTAREA input, the checked values just disappear on page refresh. That's expected since the lack of a parent form should eliminate the memory of the checkbox values, right? Well, when I dynamically add '''both''' an INPUT element and a TEXTAREA element it goes right back to remembering '''and''' moving the checked value, but only by one step. By comparison, if the checkboxes and the dynamically added form fields are contained with a form the checked value will move by a number of steps equal to the number of dynamically added form fields. Strange, strange behavior I can't really decode with certainty across the entire range of possible scenarios...