Java EE. Error handling

errorHandler.jsp

<%@ page language="java"
    contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"
    errorPage="errorHandler.jsp" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Bad Page</title>
</head>
<body>
    <%
        if (request.getParameter("notSetYet") == null)
        {
            throw new IllegalArgumentException("Not Set Yet is "
                + "Not Yet Set As Expected!");
        }
    %>
</body>
</html>

alwaysThrowsException.jsp

<%@ page language="java"
    contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"
    isErrorPage="true" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type"
    content="text/html; charset=ISO-8859-1">
<title>Our bad!</title>
</head>
<body>
    <%@ include file="header.jsp" %>
    <table style="width:100%;">
        <tr>
            <td style="width:25%;height:80%;" valign="top">
                <%@ include file="navbar.jsp" %>
            </td>
            <td style="width:75%;height:80%;">
                <h1>An Error has occurred!</h1><br>
                <%
                    out.println(exception.getMessage());
                %>
            </td>
        </tr>
    </table>
    <jsp:include page="footer.jsp" />
</body>
</html>