For the average web app, this is a desirable feature. But when combined with the ASP.Net viewstate model, it is anything but desirable, as ASP.Net uses a hidden form field to store serialized viewstate information.
The specific bug I have encountered is when using ASP.Net in conjunction with the built-in validation controls and AJAX. When using validation controls, if viewstate does not match that which last left the server, an error is produced :
The state information is invalid for this page and might be corrupted.
Because Firefox attempts to fill in the current form with current values after a refresh, a new viewstate, representing a fresh page, can be overwritten by an old viewstate (the result of 1 or many AJAX postbacks changing control states since the last "fresh" page load.)
The easiest solution I have found to this problem thus far is to change the form ID with each (non postback) page load. This will fool Firefox into thinking the form is different, and as such all values (including viewstate) will get their values from the incoming HTML rather than the browser's previous state.
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not Me.IsPostBack Then
Me.form1.ID = "form" & Date.Now.Ticks().ToString()
The only potential problem you could encounter with this solution is where the form ID has been hardwired in your application, either in client side script or server side code. This can be mitigated by always using myForm.clientID when referencing the form's ID. This is good practice in any case.
Hopefully this will help others having the same problems I was.
This solution will not work when using a Master Page. Use the solution suggested here instead (change form ID in pageLoaded AJAX event).
For those interested, the offending code is here in System.Web.UI.HtmlControls.HtmlForm.UniqueID: (from Reflector)
Public Overrides ReadOnly Property UniqueID As String
If (Me.NamingContainer Is Me.Page) Then