startssl的免费ssl证书有一年的有效期（包括登录startssl的用户登录证书和域名ssl证书）。
续期步骤为：
1）更新用户登录证书
2）更新域名ssl证书

在用户证书过期前两星期注册邮箱会收到类似提示邮件：

This mail is intended for the person who owns a digital certificate issued by the StartSSL Certification Authority (http://www.startssl.com/).
The Class 1, client certificate for xxx@xxx.com and serial number xxxxxx (xxxxx) is about to expire in about two weeks. Please log into the StartSSL Control Panel at https://www.startssl.com/?app=12 and get a new certificate for this purpose. Failing to update your client certificate might result in the loss of your account.
Should you have lost the client certificate which was previously issued to you, please register once again - login without the client certificate installed into your browser will not work in that case.

1、浏览器访问https://www.startssl.com/?app=12，如果用户证书已过期只能重新注册一个帐号了。

2、点击Validations Wizard
选择Enter Email Address。

3、输入email地址，点击Continue。

4、检查邮箱输入验证码

Complete Validation
A verification code has been sent to "xxx@xxx.com".
Please check your email account now and enter the code into the text field below.

输入验证码，点击Continue。

5、邮箱验证成功

Validation Success
You have successfully authenticated mail account "xxx@xxx.com".
You will be able to use this verification for the next 30 days, after which it expires and must be renewed.

点击Finish。

6、点击Certificates Wizard
选择S/MIME and Authentication Certificate生成登陆的证书。

7、选择要安装的邮箱

8、安装成功

Congratulations!
Your S/MIME client certificate is installed in your browser.
Backup this certificate to an external media. You may import this certificate to your mail client.

点击Finish。

9、备份用户证书
firefox：工具-选项-高级-查看证书-您的证书，下面就有需要备份的证书。
可以看到证书的有效期增加了一年（从安装成功之日起）。

10、随后更新域名ssl证书
过程和http://www.live-in.org/archives/1296.html第12步开始一样。
相同的域名要等原证书过期后才能再次申请ssl证书。
在证书过期前两星期也会收到提示邮件：

This mail is intended for the person who owns a digital certificate issued by the StartSSL Certification Authority (http://www.startssl.com/).
The Class 1, server certificate for p.live-in.org and serial number XXXXXX (XXXXX) is about to expire in about two weeks. Please log into the StartSSL Control Panel at https://www.startssl.com/?app=12 and get a new certificate for this purpose.

此时已经可以重新申请域名ssl证书了。

11、验证完域名之后
会提示：

Ready Processing Certificate
We have gathered enough information in order to sign your certificate now.
The common name of this certificate will be set to p.live-in.org.
The certificate will have the following host names supported:
live-in.org
p.live-in.org
Please click on Continue in order to process the certificate.

点击Continue。

12、提示等待人工审核

Additional Check Required!
Warning You successfully finished the process for your certificate. However your certificate request has been marked for approval by our personnel. Please wait for a mail notification from us within the next 3 hours (the most). We might contact you for further questions or issue the certificate within that time. Thank you for your understanding!