Magento admin problem

Many times it happen developer can't able to Login into the Admin even though they have entered the correct username and password
so here is the solution

1) Use 127.0.0.1 instead of localhost in your url, i.e. using

http://127.0.0.1/magento/index.php/admin instead of
http://localhost/magento/index.php/admin . we  think it will not solve our problem.

2) Running on Windows XP, I was suggested to open “host” file from
C:\WINDOWS\system32\drivers\etc and have 127.0.0.1 point to something like magento.localhost

or even 127.0.0.1 point to http://www.localhost.com . But this also didn’t work either.

3) This solution finally helped us out of this problem. The solution was to modify the core

Magento code. Open

app/code/core/Mage/Core/Model/Session/Abstract/Varien.php. Comment out the

lines 80 to 83. The line number may vary according to the Magento version. But these lines

are present somewhere near line 80. You have to comment the comma (,) in line: $this-

>getCookie()->getPath()//,

// set session cookie params
session_set_cookie_params(
$this->getCookie()->getLifetime(),
$this->getCookie()->getPath()//,
//$this->getCookie()->getDomain(),
//$this->getCookie()->isSecure(),
//$this->getCookie()->getHttponly()
);

It will help you