function CheckDomainAvailability() {
    var txtHostName = document.getElementById('txtHostName');
    var cmbTopLevelDomainName = document.getElementById('cmbTopLevelDomainName');
    if (txtHostName && cmbTopLevelDomainName) { //Check if the value is not empty/undefined
        var hostName = txtHostName.value;
        var topLevelDomainName = cmbTopLevelDomainName.value;
        document.location = '/reseller/resellerdomains?Action=CheckDomain&Domain=' + hostName + '&TLD=' + topLevelDomainName;
    }
}