We have the same problem with FF10 und Selenium 2.20.0

I've tried reverting the change to cache-control introduced in DriverServlet r15330
& recompiling, but I still have the problem.  From what I gather from the selenium-users
group, python users aren't having a problem with FF11, Selenium 2.20 and WebDriver.
 So I'm still looking for a Java-specific problem.

Using a suggestion by Svilen Ivanov (http://groups.google.com/group/selenium-users/msg/79f9d815e599ce95?&q=back)
I was able to re-use the Selenium 2.13 by manually editing install.rdf inside of webdriver.xpi
contained within the .jar file to allow it to work with FF11. 

Selenium 2.20 is still broken, but at least I have a workaround.  2.13 works for me
again.

I'm seen this on 2.21 also.

Also Noticed in 2.21

We are seeing an issue with back() navigation with Selenium 2.25 and Firefox 14. Any
updates on this fix? is it going to be part of 2.26? Chrome and IE don't seem to have
a problem, and the problem does not happen when running interactively without using
Selenium.

This also happens with Firefox 3.6. Using Firebug I could see that the first POST that
is sent as a result of a back operation, is blocked, only when using Selenium + Firefox.
Since it also happens with Firefox3.6, this likely cannot be a Firefox upgrade issue.

I switched to htmlunit 2.11 after hitting this with firefox 17.  Same problem.  Using
Selenium 2.25 java.

this was my very dodgy, very site-specific workaround:

                        // Necessary so we can come back to this page
                        // http://code.google.com/p/selenium/issues/detail?id=3611
                        String script = "var form_array = document.getElementsByTagName('form');"
+
                                        "for (var i=0, len=form_array.length; i < len;
i++) {" +
                                        "    form_array[i].setAttribute('method', 'get');"
+
                                        "}";
                        driver.executeScript(script);
                        driver.findElement(...).click();

I find this problem in FF10 with WebDriver 2.19. When I checked for the differences
in firefox preferrences settings using about:config, I could figure out that toggling
"offline-apps.allow_by_default" config removes the expired page issue. But since this
property is frozen, this can't be set in FirefoxProfile.

There is an issue with Firefox regarding document expired. Issue is caused by sites
instructing Firefox not to cache the page. When you go back to the page, Firefox honors
the site's instructions and requires you to regenerate the request. When it's a POST
request, this requires an extra confirmation.
This might be related to that:-
https://bugzilla.mozilla.org/show_bug.cgi?id=200208
https://bugzilla.mozilla.org/show_bug.cgi?id=888757

No this isn't because of a FireFox bug.  Several have stated that FireFox without WebDriver
does not have this problem.  FireFox with WebDriver with non-Java (Python) didn't have
the problem either. Back when FF10 & 11 were new they worked with 2.13.0.  Updating
Selenium/WebDriver is what broke it.  Even today FF 25.0.1 doesn't have this problem
when not under WebDriver.

Extension method which accepts this notification and allows to continue

public static void HandleDocumentExpired(this RemoteWebDriver driver)
{
    try
    {
        IWebElement error = driver.FindElementById("errorTryAgain");
        error.Click();
        IAlert alert = driver.SwitchTo().Alert();
        alert.Accept();
    }
    catch (NoSuchElementException)
    {
    }
}

Still facing this issue and Todi's code did not work for me

So I wrote a little method that first checked if element ID "errorTitle" exists. If
so it then checks for the text "Document Expired". If it finds that it then clicks
element ID "errorTryAgain". My tests now work and it is able to click try again on
the Document Expired page.

its same as Todi's code...

driver.findelement(By.id("errorTryAgain")).click();
Alert alt=driver.switchTo().alert();
alt.accept();


its working fine in my case...