As everyone knows, that default button doesn't work in FF, only IE. I've tried to put in the  tag or in the  and it's not working. I've found a js script to fix this issue, but for some reason it's not working for me. This script for a submit button, i need to use it for a LinkButton, which is should be the same.
Link:
  <div id="pnl">
    <a id="ctl00_cphMain_lbLogin" title="Click Here to LogIn" href="javascript:WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions("ctl00$cphMain$lbLogin", "", true, "Login1", "", false, true))">Log In</a>
    <input name="ctl00$cphMain$UserName" type="text" id="ctl00_cphMain_UserName" />
    <input name="ctl00$cphMain$UserName" type="text" id="ctl00_cphMain_UserName1" />
  </div>
<script>
 $(document).ready(function() {
    $("#pnl").keypress(function(e) {
        if ((e.which && e.which == 13) || (e.keyCode && e.keyCode == 13)) {
            $("a[id$='_lbLogin']").click();
            return true;
        }
    });
});
I know that i can override original function "*WebForm_FireDefaultButton*"
in This post, but i really wanted to get this one to work.
Thanx in advance!!!