Boxing champion Floyd Mayweather Jr. was booked into a Las Vegas jail Friday to serve a 90-day sentence for domestic violence against an ex-girlfriend, a term that was previously postponed so the welterweight fighter could compete in a bout. Mayweather, a flamboyant athlete regarded as the best defensive boxer of his generation, was issued standard dark blue prison garb and slippers and will be kept apart from the jail's general population of more than 3,000 other inmates, Las Vegas police said. The unbeaten Mayweather had the start of his jail term delayed in January so he could fight in a May 5 super welterweight bout.