С официального сайта:
Clone
If set Opera will copy all parameters from the specified element to the current one. If you want two elements to look the same you only have to define all parameters once and can then just clone them across to any others you specify the Clone element on.
If an option is both cloned from another element and set for the current one the cloned value will be overwritten and the element’s own setting is used.
Warning: Be careful not to create clone loops — they’ll crash Opera! ----------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Valid values: An element name
Теперь вы знаете, как закрешить оперу
