How to Clear Cookies and Cache in Safari
1. Open Safari
2. Click on the Safari menu and select Clear History.
4. In the popup window, select all history. For Safari, this is will clear the cache/cookies as well as browsing and download history.
5. Once done Quit all instances of Safari. You can do this by clicking on the Safari menu and choosing Quit.
Once this is done you can open Safari and use it as normal.