“Entertainment Tonight” co-anchor Mark Steines is calling it quits. Steines, who joined “ET” in 1995, has decided to end his run with the show. He plans to “pursue other opportunities at the end of his contract. He has been a beloved member of ‘ET’ for 17 years, and we fully support his decision,” said an “ET” rep. Steines has teamed with Nancy O’Dell, who took over from longtime anchor Mary Hart last year. No replacement has yet been named.