On: You probably don't need to validate UTF-8 strings

[cafard]

"98% of web sites are encoded in UTF8"

And quite a few web sites claim to be encoded in UTF8 and serve latin-1. It is best to check, or at least to specify error handling on your decoder.

[qbane → cafard]

My guess is that the reality is "98% of websites are valid UTF-8 documents". A large portions contain only ASCIIs so they happen to be, just indistinguishable with truly UTF8 encoded ones until they break.