odd HTML Generator.

[Garadon]

Soz don't know what to label this really, anyway I got this class function.

this.MakeGallery=function()
{
  switch(this.setup)
  {
    case 1:
    {
      id=0;
      document.writeln('<div style="position:relative;left:30px;width:500px;height:300px;background-color:#FF0000" id="gallery">');
      for(I=0;I<=2;I++)
      {
         for(J=0;J<=5;J++)
         { 				  
            document.writeln('<div style="position:absolute;top:'+(I*75+5)+'px;left:'+(J*60+5)+'px;width:55px;height:70px;border : 1px solid White;" id="'+id+'"></div>');
            id++;
         }	
      }
      document.writeln('</div>');	
      I=0;
      while(I<(6*3) && I<this.imageList.length)
      {
        var Div=document.getElementById(I);
        Div.innerHTML='<img src="'+this.imageList[I][0]+'">';
        I=I+1;
      }
    }
  }
}

Anyway that don't work gives me a null object when I reach the while loop.
But when I put
document.write('ANYTHING')
in the outer for loop it does work, any suggestions as to why?