UK online ad spend grew 17.1 percent (£540 million) through 2008 to £3.35 billion, while overall spend across media shrank 3.5 percent to £17.5 billion, the Internet Advertising Bureau says.

But that online growth has half of 38 percent posted in 2007. That’s consistent with this week’s Association of Online Publishers census, in which publishers said they expect 2009 online sales growth to be half of last year’s.

The IAB report says online now makes up 19.2 percent of all UK advertising, up from 15.5 percent the year before, and peaked at 19.8 percent during the July-December period in which the economy really began to head south. IAB UK CEO Guy Phillipson said “accountability is online advertising’s trump card” in a downturn.

—Breakdown: Within online, paid search is still king, growing 22.7 percent to £1.98 billion and taking 59.3 percent of all online ad expenditure. Web display ads grew slower, 7.7 percent to £637.4 million to 19 percent of all online ads. Unlike in print, online classifieds grew 22.2 percent to £715.2 million or 21.4 percent of online spend. Rich-media and video ads are displacing pop-ups, which will be “virtually extinct” by next year, IAB says.

—Job ads biggest: For those who thought the jobs market is rough, recruitment ads are the leading sector across search, classifieds and display combined, with 23.8 percent of all spend, followed by cars (13.5 percent), technology (11.2 percent), property (9.7 percent) and financial services (7.6 percent).

—Display ads: Ad networks now account for 44 percent of web display spend, up four percent. Entertainment and media sites accelerated their spending most, growing from 10.7 percent of display to 16.3 percent to be the highest category spender, followed by technology and finance.

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