function randInt(min,max) {
     var div = (max - min) + 1
     var randNum = Math.random()
     for (var i = 0; i <= div - 1; i++)
     { if (randNum >= i / div && randNum < (i+1) / div)
          {return i + min} } }

var header = randInt(1,4);

if (header == 1) { document.write("<a href=\"#\"><img width=\"400\" height=\"175\" src=\"http://www.campredington.com/images/gertee.jpg\" alt=\"GerTee Friendly Circular Dwellings\" border=\"0\"></a>"); }
if (header == 2) { document.write("<a href=\"#\"><img width=\"400\" height=\"175\" src=\"http://www.campredington.com/images/ricks.jpg\" alt=\"Rick's Full-Tang Knives\" border=\"0\"></a>"); }
if (header == 3) { document.write("<a href=\"#\"><img width=\"400\" height=\"175\" src=\"http://www.campredington.com/images/tjunction.jpg\" alt=\"T Junction\" border=\"0\"></a>"); }
if (header == 4) { document.write("<a href=\"#\"><img width=\"400\" height=\"175\" src=\"http://www.campredington.com/images/tims.jpg\" alt=\"Tim's Treasures\" border=\"0\"></a>"); }