// function to randomly choose pictures for central 3x3 block
// the block has npic pictures (p1..p9) and there are maxpic to choose from (named squareN.gif)
// method: store 1..maxpic in array, randomise first npic of them, the assign to image .src property

function randomisePics()
   {
   var npic = 9;
   var maxpic = 23;
   var a = new Array();
   var i, r, t;
   var v = maxpic - 0.001;
   for (i=0; i<maxpic; i++) { a[i] = i+1; }
   for (i=0; i<npic; i++)
      {
      r = Math.floor(Math.random() * (v-i)) + i;
      t = a[i];
      a[i] = a[r];
      a[r] = t;
      }
   for (i=0; i<npic; i++)
      {
      t = i+1;
      eval ('document.p' + t + '.src = "images/home/square' + a[i] + '.gif"');
      t = i+1;
      }
   }