Go step by by step and test.
Quit Safari.
Force Quit if you have to.
Hold the shift key down and relaunch Safari.
Delete Cookies
Safari > Preferences > Privacy > Cookies and other website data:
Click “Remove All Website Data”.
Empty Caches
Safari > Preference > Advanced
Checkmark the box for "Show Develop menu in menu bar".
Develop menu will appear in the Safari menu bar.
Click Develop and select "Empty Caches" from the dropdown.
Turn off Extensions if any, and launch Safari.
Safari > Preferences > Extensions
For more on this:
http://www.thesafemac.com/eliminating-browser-redirects-and-advertisements/
http://www.thesafemac.com/arg/