So you're trying to hijack a web page.

You want your program to prevent the user from going to any web pages with certain contents, and re-directing them a fixed file on their computer.

Will the user know you are interfering with their ability to browse? Will the owners of the pages know you are hijacking their viewers? If you're trying to censor a computer, why not just go buy some of the crappy software for the purpose? None of it works correctly, but it's likely to work better than a one-off you knock together.

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