使用SSL证书查看站点时出现问题

I am managing a number of websites that use SSL certificates and have had a few complaints from individuals that are not able to view some of these sites in secure mode. The problem persists regardless of browser or version that is used, does not affect viewing in non-secure mode, and only occurs with a few of the secure sites, not all. Each site has a separate SSL certificate.I am managing a number of websites that use SSL