I have a couple of 'golden nuggets' of advice that I've regularly passed on to travellers over the, almost, twenty years that I've been a travel journalist. I'm just going to mention one of them again....
Never buy anything but the most simple travel components online.
Low-cost flights, basic hotel bookings, simple city break packages for two... are generally ok (especially if you actually have first hand knowledge of the accommodation or destination)
...but never buy anything more complex online, like multi-leg flights or a family beach holiday. Always do the research online and then book it through a human.
It's not just to avoid the laughable pitfall of booking the wrong thing - this week's humerous Internet mis-booking story in the press is about the Norwegians who ended up in Rodez in France, instead of Rhodes - it's because computers can't anticipate the things you expect, or need to consider. There simply isn't a select-best-hotel-based-on-possibility-of-aunt-joining-us-midweek button on an internet booking form. Nor do computers have personalised expert knowledge - that's why travel agents were invented!
The only reason for booking travel online is to make life easier and reduce costs for the travel company, if that's what you want to do. That's why companies make it difficult to use the phone or charge you extra for it (like British Airways who add a £15 per person surcharge for telephone bookings).