[TwoD]

The code for showing an image,
for example:

Code:

document.getElementById('imageId').style.display="";

needs to be placed right after

Code:

xmlHttp.send(null)

and the code to hide it again,
for example

Code:

document.getElementById('imageId').style.display="none"

needs to be placed after

Code:

document.getElementById("txtHint").innerHTML=xmlHttp.responseText