function checkRegisterForm() {
        var user_reg = /^[a-zA-Z0-9]{3,10}$/;
        var passwd_reg = /^.{6,20}$/;
        var userp = document.getElementsByTagName('p')[1];
        var passwordp = document.getElementsByTagName('p')[2];
        var passwordp2 = document.getElementsByTagName('p')[3];
        var username = document.getElementById('username');
        var password1 = document.getElementById('password');
        var password2= document.getElementById('password-2');

        if ( user_reg.test(username.value) != true || passwd_reg.test(password1.value) != true ||  password1.value != password2.value  ) {
            if (user_reg.test(username.value) != true) {
                if (document.getElementById('user_info') == null) {
                    var user_info = document.createElement('span');
                    user_info.id = 'user_info';
                    user_info.innerText = '用户名必须是3-10位英文字母或数字;';
                    user_info.className = 'color_red';
                    userp.appendChild(user_info);
                }
            } else {
                if (document.getElementById('user_info')) {
                    userp.removeChild(document.getElementById('user_info'));
                }
            }

            if (passwd_reg.test(password1.value) != true) {
                if (document.getElementById('password_info') == null) {
                    var password_info = document.createElement('span');
                    password_info.id = 'password_info';
                    password_info.innerText = '口令必须是6-20位;';
                    password_info.className = 'color_red';
                    passwordp.appendChild(password_info);
                }
            } else {
                if (document.getElementById('password_info')) {
                    passwordp.removeChild(document.getElementById('password_info'));
                }
            }
            if (password1.value != password2.value) {
                if (document.getElementById('password_info2') == null) {
                    var password_info2 = document.createElement('span');
                    password_info2.id = 'password_info2';
                    password_info2.innerText = '两次输入口令必须一致;';
                    password_info2.className = 'color_red';
                    passwordp2.appendChild(password_info2);
                }
            } else {
                if (document.getElementById('password_info2')) {
                    passwordp2.removeChild(document.getElementById('password_info2'));
                }
            }
            return false;
        }
    }