Yesterday Google announced financial results for Q2, which ended June 30.

Revenues totaled $5.37 billion, a 39 percent increase compared to 2Q07, and three percent growth over 1Q08.

Traffic acquisition costs (TAC) totaled $1.47 billion — 28 percent of ad revenues. Operating income was $1.58 billion (29 percent of revenues), compared to GAAP operating expenses of $1.55 billion (30 percent of revenues) in Q1. GAAP net income totaled $1.25 billion, compared to $1.31 billion last quarter.

Google-owned sites drew revenues of $3.53 billion — 66 percent of total revenues — a 42 percent increase over 2Q07 and 4 percent over 1Q08. Partner sites, such as AdSense programs, drew $1.66 billion, 31 percent of total revenues. And international revenues totaled $2.80 billion, 52 percent of total revenues in Q2 compared to 48 percent in 2Q07 and 51 percent in 1Q08.

CEO Eric Schmidt reported "Strong international growth as well as sustained traffic increases on … web properties … despite a more challenging economic environment." Listen to an earnings webcast at the Google investor site.

After hours on Thursday, Google's stock tumbled 8 percent, or $40, for failing to meet investor expectations for earnings per share. (EPS totaled $4.63; analysts expected $4.74.) Paid clicks and AdSense revenue also failed to bloom: aggregate clicks, including those on Google sites and partner sites, increased 19 percent over 2Q07 but decreased one percent over 1Q08.

A representative for Google admitted the company suffered "softness" in click-through rates for sub-sectors like home finance, but advertising elsewhere was compensating. Mobile search and mobile advertising also fared well.