Frontend blank after upgrading magento

Last day I tried to upgrade my magento version 1.3.3 to 1.5.X. I did upgrade successfully my backend was working fine. But my frontend was empty. It shows blank page. I stuck up with this issue. After a day spend i went to index.php page and enabled

ini_set('display_errors', 1);

Then I cleared the cache it shows few errors. I resolved all the issues and now my frontend works fine.