It has been talked a lot that people are experiencing issues with their user's sessions on their drupal sites in Safari. Most experience the same issue:

• A user logs in, tries to create content and are kicked / logged out and taken to the homepage

It appears the bug has something to do with the way Safari handles URLs (Domain Names). For most localhost environment set ups, its easy to put whatever we would like as our site domain. But there is a problem when it comes to adding (_) verse (-) in those names.

For Example:

• localhost/mywork_sitename: This would cause a problem in Safari because an underscore is not considered a valid character.
• localhost/mywork-sitename: This would correct the sessions issue. Safari interprets this as valid and this fixes the session issue experienced.

So, if you are experiencing issues with your sessions being terminated for an account in your development environments for specific browsers, insure that your URLs (Domain Names) are valid. It fixed most issues in Safari for users experiencing the same bug.

Solution originally discovered by Nestor Mata.