autocompletemagento admin login problem off

After install magento in your localhost if you want to login or go to admin panel :
http://localhost/magento/admin
then some time you faces problem to login
this is not admin id password problem if you give correct admin and password.
Then what is prblem and how you solved.
Problem solved by this way :
http://127.0.0.1/magento/admin
or try

http://127.0.0.1/magento/index.php/admin

http://localhost/magento/index.php/admin

Problem should solve.

But in new release of magento it may not’ solve then another way of solution is

1.Try to open admin panel in opera or Apple-Safari it will work perfect here.

Third way efficient good

appcodecoreMageCoreModelSessionAbstractVarien.php
Go to line 96 or locate the code similar below:
if (isset($cookieParams['domain'])) {
    $cookieParams['domain'] = $cookie->getDomain();

Replace the code found in line 96 with this one:
if (isset($cookieParams['domain']) && !in_array("127.0.0.1", self::getValidatorData())) {

}more see:

http://mysillypointofview.wordpress.com/2010/03/24/how-to-fix-magentos-admin-login-failing-no-error-message-on-localhost/