Thanks for the hint :)
Problem solved. Actually i was working on some existing form so the textfields that were present in the form were not originally created by me and this was the problem :
<input name="firstname" class="input_bgr" id="firstname" style="text-transform:uppercase" onblur="isUpper(this)" size="12" maxlength="20" />
I changed it to
<input name="firstname" type="text" id="firstname" style="text-transform:uppercase" onblur="isUpper(this)" size="12" maxlength="20" />
And now its available in the list.
Thanks