I'm coming back to a project after a 3 month distraction. This code *was* working ... x = parseInt (x); window.alert ( x ); if (x != Number.NaN){ this.divObj.style.pixelLeft = x; } the problem occurs when x is NaN (javascipt speak for not-a-number). the if statement use to catch it - now it does not. Any clue as to why? James.