This document explains how to clear the cache and cookies in Opera 28.0
Click on Opera and then click on Clear Private Data....
From the "Obliterate the following items from:" drop down menu, choose the beginning of time. Then check Empty the cache and Delete cookies and other site data. Lastly as the final step, click on Clear Browsing Data.
You will need to restart your browser for the changes to take effect.
This document explains how to clear the cache and cookies in Opera 10.50+.
Click on Tools > Delete Private Data....
Check Delete temporary cookies and Delete all cookies, then click on Delete.
You will need to restart your browser for the changes to take effect.