var invalid_fields = new Array();

function display_error(){       
    var error_message = "Please fill in the following fields:\n";
    for (var i=0; i < invalid_fields.length; i++){
        error_message += "\t" + invalid_fields[i]  + "\t" + "\n";
    }
    alert(error_message);
}

function formCheck() {

regCheck = /^([a-zA-Z0-9])+([\.a-zA-Z0-9_-])*@([a-zA-Z0-9])+(\.[a-zA-Z0-9_-]+)+$/

    if (document.ts_form.txtfname.value == "") invalid_fields[invalid_fields.length] = "First Name";
    if (document.ts_form.txtlname.value == "") invalid_fields[invalid_fields.length] = "Last Name";
    if (!regCheck.test(document.ts_form.txtEmail.value)) invalid_fields[invalid_fields.length] = "Email";
    if (invalid_fields.length > 0){
        display_error();
        invalid_fields = new Array();       
        return false;
    }
    else return true;
}