More UK web users visit Google than any other site, with nearly nine out of 10 logging in to the search site last month according to internet analyst comScore.
Google had 28 million visitors in May, reaching 89 percent of UK web users aged 15 or older, beating Microsoft, which had 27.4 million visitors and a reach of 87 percent.
Auction site eBay, Yahoo and the BBC made up the rest of the top five sites visited by UK users last month, comScore reported.
The figures show a seasonal increase in visits to travel booking sites, prompted by the May bank holidays, with Priceline.com, First Choice Holidays, EasyGroup, and TUI Group - parent firm of Thomson Holidays - all showing an increase of between 13 and 17 percent on April figures.
The Weather Channel was the UK.'s fastest growing internet site, up 36 percent in May to 2.4 million visitors.
Social networking site Facebook - subject of much recent media interest - saw visitor figures up 30 percent from April to 4.8 million visitors, its third consecutive month with an increase of 30 percent or more. In May 2006, the now-trendy site had just 216,000 unique visitors.
The figures also showed a surge of interest in Channel 4, driven by the start of a new series of Big Brother, along with Top Shop's parent firm Arcadia Group.
The comScore top 20 websites
1. Google sites
2. Microsoft sites
4. Yahoo! sites
5. BBC sites
6. Ask Network
7. Time Warner Network
8. Fox Interactive Media
9. Amazon sites
10. Wikipedia sites
11. Lycos Europe sites
17. Home Retail Group
18. Gorilla Nation