function toggleDisplay(tag_name,class_name) {
coll = document.getElementsByTagName(tag_name);
for (i=0; i<coll.length; i++){ 
  if (coll[i].className == "tsk") { 
    coll[i].style.display = ( coll[i].style.display == 'block' || coll[i].style.display == '' ) ? 'none' : 'block';
  }
}
} //end function