Webb, who won the Kraft Nabisco Championship earlier this year, is 12-under 204, and has a one-stroke lead over Michelle Wie, who shot 70 Friday.
"I think with a one-shot lead, it does not really feel like you are in the lead," Webb said. "There are a lot of great players behind me and you feel like you still have to attack the course as aggressively because it is not like I have a three or four shot lead. It is still anybody's tournament."
Wie is alone in second at 11-under 205.
Laura Davies (67) and Se Ri Pak (70) are tied for third at 10-under 206.