Two strokes better than Dorothy Delasin (71), Webb was one of only four players to be under par through 36 holes at the Hiddenbrooke Golf Course at Vallejo, Calif.
In joint third at 2-under for the event sat overnight leader Se Ri Pak (72) and Rachel Teske, who reached the mark with a brilliant 65.
As good as Teskes round was, Webbs might have been even better on Friday.
The 26-year-old birdied her first two holes of the day and followed them up with three more red numbers over her front nine to go out in 5-under 31.
After a bogey at No. 10, she immediately responded with three consecutive birdies from the 11th through the 13th holes to get to 7-under for the round, but then found trouble at the par-4 14th, where she carded a triple-bogey.
A final birdie at the par-5 16th healed the wounds slightly, and in the end, she was in with 67.
Click Here to See Karrie Webb's Scorecard.
Webb is looking for her third win on the year. While her first two victories on the season both came at major championships, the season has been a far cry from her 2000 campaign, which saw her win seven times on the LPGA Tour.
Annika Sorenstam has stolen most of the headlines thanks to five wins on the year, but the Swede will need to turn on the heat over the weekend for another victory.
She shot 72 on Friday to be at 1-over entering the weekend.
Meanwhile, defending champion Juli Inkster is tied for fifth at even-par, five strokes off the pace in this limited field of 20 of the tours best players.
Click Here for Full-Field Scores from the Samsung World Championship.