You have to go to your DB and enter in the core_config_data table.

Under this table you have to find under the path column

web/unsecure/base_url and web/secure/base_url

and edit the value column with the correct url {{base url}} or with the Url of your magento (ex. http://www.yoursite.com)

Oppure cambiarli nell'admin sotto "Sistema > Configurazione > Web" in "Sicuro" e in "Insicuro"