CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]
Revenue	$ 45,192	$ 39,670	$ 130,917	$ 114,934
Costs and expenses:
Cost of revenue	10,597	9,036	31,342	25,450
Sales and marketing	16,141	12,713	46,118	36,820
Product development	10,023	8,005	27,091	21,881
General and administrative	9,508	7,316	29,581	22,784
Amortization of purchased intangibles	224	11	672	98
Total costs and expenses	46,493	37,081	134,804	107,033
(Loss) income from operations	(1,301)	2,589	(3,887)	7,901
Other income	209	41	264	155
(Loss) income before (benefit from) provision for income taxes	(1,092)	2,630	(3,623)	8,056
(Benefit from) provision for income taxes	(362)	1,030	(832)	3,193
Net (loss) income	$ (730)	$ 1,600	$ (2,791)	$ 4,863
Basic net (loss) income per common share (in dollars per share)	$ (0.01)	$ 0.03	$ (0.05)	$ 0.09
Diluted net (loss) income per common share (in dollars per share)	$ (0.01)	$ 0.03	$ (0.05)	$ 0.09
Weighted average shares outstanding used in basic net (loss) income per common share calculation (in shares)	54,046,161	55,688,824	54,898,974	55,087,109
Weighted average shares outstanding used in diluted net (loss) income per common share calculation (in shares)	54,046,161	57,760,868	54,898,974	56,987,302