Hey guys...
few days back i was trying to customizing the login portlet of IBM.
So i kept my own login portlet on login page along with IBM's login portlet.
I was able to login with my login portlet and were doing some code changes to meet customized requirement. To test something i deleted IBM's login portlet and somehow i was also not able to login with my own login portlet. i got stuck but then any how i have to login to add IBM's login portlet back on login page.
Then i posted this issue on IBM developer works's and got the solution which is a standard IBM portal login url.
With this url i was able to login and put IBM's login portlet back on login page.
I wasted my 30 minutes in finding solution and waiting for developerworks response to my thread.
Also the reason for writing this post, to save time of all who might got this issues in their env.

Here is the IBM Portal login URL
because of shot space, i have just breaked up in three lines to get proper url

http://servername:port/wps/portal/cxml/
04_SD9ePMtCP1I800I_KydQvyHFUBADPmuQy?userid=<userid>&password=<password>

But yes.. i got my customized login portlet working now and it's being used in PROD now. :-)