some times Internet Explorer cached the ajax requests and it creates problems .i used prototype library for a an ajax request .it works fine for firefox and opera.but creates problems with IE 7.then i add useless date value to query string for making the request unique .It solves my problem.and works fine .

the example code :

var date=new Date();

new Ajax.Request(’sample.asp?id1=’+Current_Id+’&id3=<%=IdCategoria%>&id2=’+id2+ ‘&date=’+date.getTime(),
{
method:’get’,onSuccess: function(transport)
{

}

}