WEST LM BEACH, Fla. An unexplainable mental error cost Karrie Webb sole possession of the lead today at The Office Depot, the third LPGA event of the 1999 season. She hopes it won't cost her the tournament.

Webb inadvertently put the blade end of her 6-iron on the ground inside a red hazard line after hitting her drive right of the 17th fairway, leading to a two-stroke penalty and putting her in a three-way tie for first with Dottie Pepper and Juli Inkster.

"I just wasn't thinking,'' said Webb, a 24-year-old Australian who was the LPGA Rookie of the Year in 1996. "There's no excuse ... it was a mental error.

"At least it didn't cost me the tournament. There's still one round to go. I'm still in contention.''

Webb's ball had come to rest in a muddy area with about three-quarters of it showing. She immediately picked up her club, realising she had made an error. It was too late. She was penalised two strokes for grounding her club in a hazard.

As a result, she finished the day with par 72 rather than the 2-under-par 70 and the two-stroke lead that had seemed likely.

"It's too bad,'' said LPGA rules official Jane Reynolds who met Webb in the scoring tent behind the 18th green after the round had been completed. "We hate to see things like that happen. I'm sure she didn't intend to do it. Unfortunately, intent is not part of the rules.''

Pepper made five birdies and a bogey on the 6,277-yard Legend course and Inkster made four birdies and three bogies to tie Webb at 208 after 54 holes.

"You hate to see something like that happen,'' Inkster said of Webb. "But in the heat of battle, sometimes strange things occur.''

It was the second year in a row that the leader here was penalised for a rules violation. Last January, Wendy Ward was assessed two strokes when she and her caddie took an unauthorised shuttle ride from the 18th green to the first tee during the second round.

Webb had four birdies and two bogies on the first 11 holes and looked poised to take sole possession of the lead for the first time at the tournament.

Webb and Inkster were tied after the first round with 67s. Webb and Betsy King shared the second round lead at 136. King faded today with 77 and was tied for 11th.

"I'm playing well, but the greens have dried up since I played the Legend on Wednesday,'' Webb said. "If they stay this firm tomorrow, it will take some patience to score well.''

Patty Sheehan and former champion Kelly Robbins are a stroke back at 209 after posting 71 and 72.

The final round was scheduled Saturday, a day earlier than usual, to avoid conflict with the Super Bowl, which is being played in Miami on Sunday. The field includes 78 top money winners from 1998 and two sponsor exemptions. There was no cut.