function imgSrcReplace(a, b) { 
var imageTags = document.getElementsByTagName("img");
for (var i = 0; i < imageTags.length ; i++)
{
  //alert("src of this a element is : " + imageTags[i].src + "\n");
    imageTags[i].src = imageTags[i].src.replace(a, b);  
}
};