On the IIS 7 sometime you would find the SSL binding for the website has been deleted and not replaced, or has been deleted and replaced with invalid certificate info.  The problem occurs because of a legacy SSL certificate hash property interfering with the current SSL binding, resulting in the correct binding being deleted.

And sometime  following entry is logged in the event viewer

Log Name:      System
Source:          Microsoft-Windows-HttpEvent
Date:              3/31/2010 2:43:28 PM
Event ID:         15300
Task Category: None
Level:             Warning
Keywords:      Classic
User:             N/A
Computer:      IISServer
Description:
SSL Certificate Settings deleted for Port : x.x.x.x:443

For the Fix

Read KB article 2025598