Firefox help needed

[dofinch-smokie at yahoo.co.uk]

Here's an oddball. I'd really appreciate some help.

My network uses a wireless router which works fine in
almost all respects. It's managed using a web-browser and
here there IS a problem. 
 
The firmware sends html pages to the browser and uses
Javascript. Unfortunately there is a bug in the firmware
which causes the device to send html which tries to define a
Javascript function without a name! Here is the code snippet:
 
function (F)
{        
    if (F.wl_passphrase.value == "")
    {
        alert("Please enter a Passphase!");
        F.wl_passphrase.focus();
        return false;
    }
        F.submit();
}
 
I am running Firefox 3.6.2pre under Ubuntu 9.10. When the
browser encounters this declaration it writes a syntax error
in the Error Console and seems to stop doing Javascript.
Anyway the page only partially loads. Exactly the same
behavior occurs with the previous version (3.5) that I was
running.
 
If I copy the page source to disk and delete the above
snippet, the page loads properly into Firefox.

Now here's the HARD part. IE7 carries on executing
Javascript after encountering this syntax error. 

There is NO firmware upgrade available to me for this
router! Aaaaaaggggghhhhh! So I'm having to boot up an
ancient Windoze to manage my router!! So here's where I
would be grateful for lots of help!!

1) Advice on any switches/settings that can be used to get
Firefox to ape the above Internet Explorer behaviour.
2) Advice on a proxy which can be run in Ubuntu 9.10 and
which is configurable to the extent that I could set it up
to delete the above code as it passes on to the browser.
 
Thanks a LOT in advance.
 
Geoff