My test ie6 version is 6.0.2900.2180.xpsp_sp2_gdr.070227-2254

when i do this:

$.get("/IndexAction.do",function(txt){
    alert(txt);
}

ie thorw then Automation error

when i search in jquery-1.2.3,i found this

var xml = window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest(); 

then i modify it:

try {
    var xml = window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
}
catch(e) {
try
{
    xml=new ActiveXObject("MSXML2.XMLHTTP");
}
catch(e2)
{
try
{
    xml=new ActiveXObject("MSXML3.XMLHTTP");
}
catch(e3)
{
    alert("It's all error");
}
}	
}