I cannot login to the Magento Admin - what can I do?

Sometimes you have the problem that you cannot login to the Magento Admin area - despite entering the correct username and password. There are several points that you can check in this case (it is most probably an issue with the cookies):

• Check the cookie domain in the core_config_data table that it matches your backend domain
• Also check that if you previously switched from HTTPS to HTTP that you drop all browser cookies, as if the adminhtml cookie already exists with the "Secure" flag, it cannot be overwritten