Hi naveed,
<script type="text/javascript">
$(function () {
$('[id*=lbtnSearch]').attr('disabled', 'disabled');
$('[id*=txtSearch]').keyup(function (event) {
if ($(this).val().length <= 3) {
$('[id*=lbtnSearch]').attr('disabled', 'disabled');
$('[id*=lbtnSearch]').removeAttr('href');
$('[id*=txtSearch]').keypress(function (event) {
if (event.which == '13') {
event.preventDefault();
}
});
}
else {
$('[id*=lbtnSearch]').removeAttr('disabled');
$('[id*=txtSearch]').keypress(function (event) {
if (event.which == '13') {
event.preventDefault();
$(this).unbind(event);
}
});
}
});
});
</script>
Check with the above script.