There is no evidence that a deterrent like this works, we will never know who might have been radicalised but was not because they were deterred from visiting extremist websites. However if those visiting these websites really are terrorists then a spell in prison is not going to deter them. Moreover this is not a good way of preventing radicalisation as it does not get to the key issues. Instead of prosecuting those who visit extremist websites they must be shown how those views are wrong, something that can only be done through debate and discussion, [1] locking them up will not do this.  [1] Rothschild, Nathalie, ‘How can debate challenge extremism?’, guardian.co.uk.