in the first i prefer using Jquery ,
you must add jquery library befor <script> tag that contain on this code.
<script src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.10.2.min.js">
</script>
function hideBusActivityECommerce()
{
myActivity = getActivity();
if(myActivity =="ECommerce")
{
$("#"+document.getElementById('<%=ECommerceSection.ClientID%>).style.display = 'inline';
$("#"+<%=ddl_submission.ClientID%>).val("");
$("#"+<%=ddl_submission.ClientID%>).attr("disabled","true");
}
else
{
$("#"+<%=ECommerceSection.ClientID%>).css("display","none");
$("#"+<%=ddl_submission.ClientID%>).attr("disabled","false");
}
if(myActivity=="ECommerce" || myActivity=="Retailer Owned")
{
$("#"+<%ctl00_ContentPlaceHolder1_Tab2b_cb_Non%>).attr("disabled","false");
$("#"+<%ctl00_ContentPlaceHolder1_Tab2b_txt_NonMerchantNo%>).attr("disabled","false");
$("#"+<%ctl00_ContentPlaceHolder1_Tab2b_txt_rate%>).attr("disabled","false");
}
}