Several apps and sites like longform and readability offer users a "read view" of other sites, which includes stripping the content of ads and changing font to make the text easier to read. I am working on a similar concept and wanted to check what legal issues are involved with doing that.
As long as the user is entering the URL, there's no possible way you could be violating anything. Here's the process at a high level:
Site owner makes content available to public, with TOS which may or may not be binding on the end user.
End user accesses aforementioned content.
End user processes it using your application, with TOS which may or may not be binding on the end user.
As long as your application isn't illegal per se, then you can't be responsible for the possibility that your users may use it against the TOS of the original site. Want some more protection? Put a clause in your TOS that advises users that they should consult the TOS of the target site before using your application to ensure they aren't violating those TOS, and that you disclaim all liability in the case that your application is used improperly.
Can your application be considered illegal per se? I highly doubt it. All you have there is a browser that doesn't fully render HTML pages. Want to be completely and utterly blameless? Make the full HTML available by viewing page source.
I am not a lawyer, I am not your lawyer. THIS IS PERFECTLY LEGAL.
(If your application points at a specific list of sites specified by you, whether configurable or not, this answer might change. If the user is the one supplying the URLs, see above).