error :id is already registered

Question

i have this error in my code

Error: Tried to register widget with id==legend1 but that id is already registered

the code for the legend is:

    <div id="legend1"></div>

    var stackedAreaLegend = new dojox.charting.widget.SelectableLegend({
    chart: chart1
    }, "legend1");   

   stackedAreaLegend.refresh(); 

how i can solve this error?