This is the example to how to do Ajax call to read message in HTML using JQuery.

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

function ReadMessageCall() {

var pageUrl = '<%=ResolveUrl("~/WebService/Webservice1.asmx")%>'

$.ajax({

type: "POST",

url: pageUrl + "/ReadMessage",

data: "{'mail':'" + $('#<%=txtemail.ClientID%>').val() + "'}",

contentType: "application/json; charset=utf-8",

dataType: "json",

success: OnSuccess,

error: OnError

});

}

function OnSuccess(response) {

$('#<%=lblMessage.ClientID%>').html(response.d);

}

function OnError(response) {

alert(response.status + " " + response.statusText);

}

</script>