Opera mini and back button

hi all,
       Actually i don't know where is best place to write about this type of problem.i have built up an online exam application.when user click back button he will be shown his previously answered question but in read only mode.i have used Script Manager control's Onnavigate even handler.it works fine in all web browser except 'Opera Mini' mobile browser.How can i control Opera Mini's back button.Actually users will answer to these questions througn mobile. 
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