<select id="country" onchange="FillData(this.value)">

    <option value="-1">Select</option>

    <option value="Israel">Israel</option>

    <option value="USA">USA</option>

</select>

<select id="City">

</select>

function FillData(country) {

    if (country.value != "-1") {

        var xhr = new XMLHttpRequest();

        xhr.onreadystatechange = function() {

            if (xhr.readyState == 4 && xhr.status == 200) {

                ClearCity();

                FillCity(xhr.responseText);

            }

        }

        xhr.open("GET", "Handler1.ashx?country=" + country, true);

        xhr.send();

    }

}

public void ProcessRequest(HttpContext context)

{

    context.Response.ContentType = "text/plain";

    if (context.Request["country"] == "USA")

    {

        context.Response.Write("NY;Washington");

    }

    else

    {

        context.Response.Write("tel aviv;beni brak;ramt gan");

    }

}

function FillCity(responseText) {

    var city = document.getElementById('City');

    var array = responseText.split(';');

    for (var i = 0; i < array.length; i++) {

        var item = document.createElement("option");

        item.text = array[i];

        city.add(item);

    }

}

function ClearCity() {

    var city = document.getElementById('City');

    for (var i = city.children.length; i >= 0; i--) {

        city.remove(i);

    }

}

window.location.hash = country;

 onhashchange="HashChangeHandler();

function HashChangeHandler() {

    var country = document.getElementById('country');

    var hash = window.location.hash;

    if (hash == '#' || hash == '') {

        country.value = "-1";

        ClearCity();

        return;

    }

    if (hash.substr(1) != country.value) {

        country.value = hash.substr(1);

        FillData(country.value);

    }

}