If your daughter is really technology-savvy, then your best methods will be an inconvenience at best.
That said, I use a combination of OpenDNS, Adblock Plus and the Firefox extension Procon Latte.https://addons.mozilla.or...refox/addon/procon-latte/
It can be locked down pretty tightly, supports whitelists, blacklists, objectionable-word replacement, all kinds of stuff.
On Chrome, Foxfilter does alright, but it costs $9.99 a year to get it password-protected.http://www.inspiredeffect.com/FoxFilter/
If you use OpenDNS, make sure you use the dynamic IP update service, and make sure your router doesn't insert a third DNS entry, because if a DNS lookup fails for any reason, the third entry will then allow access.http://www.opendns.com/support/dynamic_ip_tech/https://forums.opendns.co...nts.php?DiscussionID=1684
K9 looks pretty good, but is Windows and Mac only (not hatin', just sayin'...) so my solutions apply to Linux users as well.
If you ever want to lock down a Linux computer beyond browser plugins, it'll get complicated, but routing access through a proxy running DansGuardian is a good choice.http://dansguardian.org/?page=whatisdg