function showIframes(){
var iframefirst = document.getElementById('iframefirst');
if(iframefirst){
iframefirst.innerHTML = '';
}
var iframesecond = document.getElementById('iframesecond');
if(iframesecond){
iframesecond.innerHTML = '';
}
var iframethird = document.getElementById('iframethird');
if(iframethird){
iframethird.innerHTML = '';
}
}