"Oh my gosh, looking at all of these amazing structures, the history that you could still visually appreciate from thousands of years ago with modern life going on all around it - I just thought it was magical," Kaufer said of his 1989 visit to Israel.

"It instantly turned into my favourite trip then and ever since."

The holiday is etched in Kaufer's memory for another reason: It was the honeymoon he took with his young wife, Caroline Lipson Kaufer. She died in 2005 of pancreatic neuroendocrine cancer at age 42, leaving Kaufer with four young kids to raise on his own.

The 52-year-old is not your typical tech company CEO. He's gray-haired and more understated than the head of a public corporation.

Though he runs a travel website, Kaufer doesn't really suffer from wanderlust, preferring to stay close to his home in the Boston suburb of Newton, Massachusetts.

That's probably a good thing for his family because after he remarried in 2012, he and his wife, Lisa Howe, found themselves with a Brady Bunch-style household: eight kids between the two of them.

After Kaufer sold his company in 2004 for $210m (£134m), instantly transforming him from a middle-class guy to a wealthy one percenter, his idea of splurging was to trade in his old clunker for a new Volkswagen Passat, put away money for his kids' college educations and make several sizable donations to medical research.

"I wanted to use the windfall to take care of my family," Kaufer said. "I don't fly private jets."

Aside from that Israel visit, the other trip that stands out in Kaufer's mind - and the one he's most accustomed to recounting - is the holiday he and Caroline decided to take to Mexico in 1998.

In planning for the trip, Kaufer began searching the internet for objective reviews about a particular hotel, but all he could find were dozens of websites with the same promotional boilerplate and publicity photograph.

When he finally unearthed a genuine review by a couple who had stayed at the hotel, Kaufer found their unvarnished perspective - and the uninviting photographs they posted - invaluable. He booked another hotel instead.

Caroline, a Harvard Business School graduate and a software executive in her own right, suggested there could be a start-up in matching up travellers with helpful, honest reviews.

Kaufer, who recently had sold the software company he co-founded after graduating from Harvard in 1985 with a degree in computer science, was game. In 2000, TripAdvisor was born.

Today, the Newton-based company with 2,900 employees features some 225 million user-generated reviews and offers direct bookings for hotels, vacation rentals, flights and restaurants.

TripAdvisor.com averages 340 million unique monthly users, making it the world's largest travel site, according to comScore Media Metrix.

Though Kaufer sold the company in 2004 to InterActiveCorp, which at the time also owned Expedia, he stayed on as CEO - even after TripAdvisor came under Expedia's umbrella in 2005 and was spun off from Expedia as an independent public company in 2011.

At its initial public offering, TripAdvisor opened at $29 (£19) a share. After peaking about a year ago near to $110 (£70), it's now trading around $75 (£48).

The period of acquisitions coincided with turmoil in Kaufer's own life, after his wife died of cancer and he was forced to rely on friends and family for help raising his children, then aged five, seven, 12 and 13.

Kaufer had hired help at home, but he made a point of making it back to the house every night to eat dinner with his kids.

Kaufer says the Jewish value of leaving the world a better place helps guide his life, even though he can't remember the Hebrew term for it (tikkun olam).

"We try to practice it as a family and as a company," Kaufer said.

He created a charitable programme at TripAdvisor that donates two per cent of all profits to charities suggested by company employees.

In 2013, the last year for which records are publicly available, the TripAdvisor Charitable Foundation gave away nearly $2.7 million (£1.7m).

Raised in Los Angeles, Kaufer grew up going to a Reconstructionist synagogue, with his family lighting candles on Friday nights and celebrating the major holidays.

His father had been raised Orthodox, but Kaufer's upbringing was more Zionist than observant.

He remembers his parents going to Israel shortly before the outbreak of the 1973 Yom Kippur War and returning home with a shovel filled with shrapnel holes as a souvenir from the battlefields of the Golan Heights.

Kaufer's own family belongs to a Reform synagogue, Temple Beth Avodah in Newton, and his kids spend summer at Crane Lake Camp, a Reform movement camp in the Massachusetts Berkshires.

His son, Harry, graduated from Brandeis, the Jewish-sponsored nonsectarian university in suburban Boston, in 2013.

Though Kaufer hasn't been back to Israel since his visit more than 25 years ago, most of his children have, including on Birthright Israel programmes and with their grandparents.

A daughter is planning on spending this summer there.

When Kaufer does travel, he says he always tries to write hotel reviews - and stay incognito so the hotels don't give him any special treatment.

"Hoteliers can get unnecessarily nervous if they hear I'm coming," Kaufer said. "To be clear: Yes, I write reviews like all their other guests, but my review doesn't count any more than anyone else's - at all."

The competitive landscape for TripAdvisor has become more intense as Google and other tech giants have crept into travel.

Competitors include Booking.com, Priceline and Yelp.

But Kaufer says he tries to keep a few steps ahead by constantly innovating - and not paying attention to the daily stock price.

"We're all doing things to constantly change our business models," Kaufer said, noting that the site expanded last year to offer instant bookings.

"But maybe somebody will get your customers anyway."

If he was ever forced out of TripAdvisor, Kaufer said, he'd probably pursue something in the medicinal life sciences.

He has special interest in cancer (after his wife's death he established the Stephen and Caroline Kaufer Fund for Neuroendocrine Research) and multiple sclerosis, which sent his mother to a wheelchair from the time Kaufer was 13.

"With TripAdvisor, it's pretty cool to have been able to affect in a positive way so many people's vacations, and to help a huge number of independent businesses that have great products or services for travellers," Kaufer said. "But it's not curing cancer."