function sm_ShowImg(imgsub,id_num,caption) {

var doc_root="smgallery";
//Change main image
var md_id="img_"+id_num;
document.getElementById(md_id).src=doc_root+"/files/images/"+id_num+"/md/md-"+imgsub;

// Change href link
var link_id="href_"+id_num;
alert("link:"+document.getElementById(link_id).href);
document.getElementById(link_id).href=null;
document.getElementById(link_id).href=doc_root+"/files/images/"+id_num+"/lg/lg-"+imgsub;

// Change caption
document.getElementById(link_id).title=caption;
}