function doOnclicks(){
	var allImages = getElementsByClassName(document, 'img', 'smallThumb');
	var len = allImages.length;
	var bigPic = document.getElementById('bigPic');
	var hiddenField = document.getElementById('picture');
	var first = true;
	if(len>0){
		 for(i=0;i<len;i++){
			var a = allImages[i];
			if(first)bigPic.src=a.src.replace('tn_','mtn_');
			hiddenField.value=a.src.replace('tn_','mtn_');
			first = false; 
			a.onclick = function() { 
				var newSrc = this.src.replace('tn_','mtn_');
				bigPic.src=newSrc;
				hiddenField.value = newSrc;					
				return false;
			 }
		}
	}
}
addOnLoad(doOnclicks);