Move over Yahoo, there’s a new display advertising champion in town, as of the first quarter of 2011. You may have heard of the company, as they’ve also been dominating the search advertising category. 

According to a new report from research firm IDC, Google’s net U.S. display advertising revenue share grew to 14.7% in the first quarter of this year, from 13.3% in the fourth quarter. Meanwhile, Yahoo!’s declined from 13.6% to 12.3%. Microsoft declined to a 6.5% market share in Q1 and Facebook rose in prominence with 8.8% of the market.

The figures are interesting as we watch Google expand the relationships it has established in search to a separate category. IDC’s Karsten Weide, who authored the report, attributes the growth to Google converting small and medium-sized businesses (SMBs) from search to display. The report noted that display’s share is growing (to 33%) while search’s share has declined from 53.4% two years ago to 48.7% in the first quarter of this year. Search ads commanded more overall revenue, though ($3.9 billion), as compared to display ($2.7 billion).

In the search business, Google’s net U.S. market share rose to 59.6% in the first quarter, up slightly from 4Q. Microsoft stayed in second place with 7.9%, up .9% from the fourth quarter, while Yahoo dropped to 7%, from 8% in the previous quarter. Yahoo’s search ad network revenue is continuing to decline, according to the report, dropping from $248 million in Q3 of 2010 to only $24 million in Q1 of 2011. 

Mobile online advertising continued to boom in the U.S. in the first quarter, coming in at $419.4 million, as compared to just $293 million in the fourth quarter, dramatically confounding the usual Q4/Q1 Boom/Bust cycle and confirming the influence of devices like the iPad, iPhone, and Android OS handsets.