Start Firefox in Use Troubleshoot Mode in Firefox to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.

See:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

The problem is there's a glitch in the javascript of http://edudel.nic.in/mis/MisAdmin/frmMisLogin.aspx There's a form element with an ID of "txtpassword", but in their validation function, they call it with getElementById("txtPassword"). Obviously a case issue, but it apparently works in IE.

I created a workaround for a user I met in #firefox, a simple greasemonkey script that replaces the function with a fixed version. Here's the link: http://userscripts.org/scripts/show/102156

You can also do such a redefine with a bookmarklet that you need to run before submitting the form.

javascript:
function test(){
 var text1 = document.getElementById('TextBox1').value;
 var text2 = document.getElementById("txtpassword").value;
 var text3 = document.getElementById("TextBox3").value;
 document.getElementById('txtpassword').value = text1+text2.substr(2,200)+text3;
 document.getElementById('TextBox4').value = text2.substr(0,2);
}

It's The Fastest Fox Add-On or at least it was in my case. Try that one first if you have it. Otherwise follow the already suggested advice, but disable Add-Ons in groups of 3 after you run in Safe Mode until you no longer have that message. Hope this helps I spent about 30 minutes figuring it out.