Shares of United Online Inc. fell 8 percent in late trading Tuesday after its longtime chief executive said he would leave the Internet services company after its FTD floral delivery business is spun off later this year.

Mark Goldston’s announcement came after the Woodland Hills company, which expanded into online retail and social networking as demand for its low-cost Internet access service declined, announced better-than-expected first quarter revenue.

The spinoff into two public companies is expected to close in the third quarter. Rob Apatoff, current president of the FTD unit, will become chief executive of FTD. United Online board’s will conduct a search for a new chief executive of United Online, which will retain its legacy NetZero and Juno Internet access services and the Memory Lane school alumni social networking site.

“I feel that when the tax-free spin off of FTD Companies is completed, it would be the appropriate time for me to move on and pursue career opportunities outside of United Online,” Goldston said in a statement.

Goldston has lead the company since 1999, when he joined predecessor company NetZero, then an upstart in the Internet access market that used price to take on larger competitors AOL and Compuserve. It changed its name to United Online after the merging with competitor Juno, and acquired FTD in 2008.