While Kingston was busy attending celebrity birthday parties for Britney's boys and Henry Klum-Samuel this weekend, Gwen Stefani and Gavin Rossdale left their sons at home to celebrate their sixth wedding anniversary on Sunday night at Osteria Mozza Restaurant. Gwen showed off her new popular "Z" and "K" necklace, along with that gorgeous hairdo you all loved, while Gavin smiled from ear-to-ear. Gwen's been laying low but of course still working — it was recently announced she's designing L.A.M.B. uniforms for the bar staff at W Hotels. So much for this couple to celebrate, although not everyone in Hollywood is as happy as these two — Gavin's daughter Daisy Lowe and Mark Ronson have recently ended their relationship.