Chained drop down box value not showing in IE 7,8,9 or lower browser

Here is my javascript code::---

<script language="javascript" type="text/javascript">



//Browser Support Code

function ajaxFunction(str){

    var ajaxRequest;  // The variable that makes Ajax possible!



    try{

        // Opera 8.0+, Firefox, Safari

        ajaxRequest = new XMLHttpRequest();

    } catch (e){

        // Internet Explorer Browsers

        try{

            ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");

        } catch (e) {

            try{

                ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");

            } catch (e){

                // Something went wrong

                alert("Your browser broke!");

                return false;

            }

        }

    }

    // Create a function that will receive data sent from the server



    var url="../frontend/views/home/category.php" + "?value="+str;



    ajaxRequest.onreadystatechange = function(){

        if(ajaxRequest.readyState == 4){

            //document.myForm.time.value = ajaxRequest.responseText;

            document.getElementById("class").innerHTML=ajaxRequest.responseText;

        }

    }



    ajaxRequest.open("GET", url, true);

    ajaxRequest.send(null); 



}





</script>