Missing Cache Validation

The site as a whole is controlled by a general cache-control and cache expiration (sometimes referred to as strong cache headers) and specific resources such as images use what is known as “weak cache headers” to validate specific resources.If there is no resource cache validation then browsers and crawlers cannot refresh the content efficiently.

This can cause a negative result from crawlers and slow the load time of a site.The cache is set in the meta data on the page where the media is located.  You should avoid linking to images, video or other media that does not have cache validation.