If-Modified-Since HTTP header informs the search engines if your pages has been modified or updated since last indexation in the search results.
In order to add it to a WordPress, you can use the plugin named “SEO-HEADERS-Easy” Protocol HTTP 1.1.
It will send to a client the correct HTTP header last modified cache control and 304 not modified.
Note: Commissions may be earned from the links above.
This page contains references to products from one or more of our advertisers. We may receive compensation when you click on links to those products. For an explanation of our advertising policy, please visit this page.