I can not sign in booking.com .. please help

1. Delete Caches.db

Close all windows and quit all applications.

Hold "option" key down and click "Go" menu in the Finder menu bar.

Select "Library" from the dropdown.

Library > Caches > com.apple.Safari > Caches.db

Right click the Caches.db file and select "Move To Trash.

Close windows and relaunch Safari.

2. 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.

3. Delete Cookies

Safari > Preferences > Privacy > Cookies and other website data:

Click “Details” button.

Remove all cookies except the ones from Apple, your ISP and banks.

Try another browser as a test.

Firefox