Magento: How to fix the cookie problem when logging or registering as a customer?

open your hosts file with notepad (or another plain text editor, do not use word!)
The location of the file is c:\windows\system32\drivers\etc\hosts

Add the ip address and the magento e-commerce URL:

example:
127.0.0.1 www.localhost.local localhost.local

save the file and open your browser with : the path(url to your magento e-commerce)
Do not forget to edit the url path(s) in admin panel under System>Configuration>Web