Sacred-texts.com has editions of both of these authors up.

Herodotus: The History of Herodotus, tr. by G.C. Macaulay. Parallel English and Greek (unicode) text. (FYI, Perseus version here)

Tacitus: The Works of Tacitus, tr. by Alfred John Church and William Jackson Brodribb. Parallel English and Latin text. (FYI, Perseus version here)

Check 'em out. If you know your citation, it may be faster to access the sacred-texts.com static copy than Perseus.