The «Last-Modified + 304 Not Modified» addon – is the instrument for online store indexation optimization. With the help of HTTP-headers, this module tells the search engine whether the requested page was modified and when precisely it was modified.
HTTP-header Last-Modified tells the browser or search machine the time of the last time the page was modified. If the browser or search machine gets the Last-Modified header then the next time you are going to ask for the address, if the page can be found in the local cache folder, it will add the request If-Modified-Since (whether the page was modified after the date received in Last-Modified). The server in its turn when receiving the request If-Modified-Since will be forced to compare the temporary note it received with the indicated time of last page modification, and in case the page wasn’t changed it will answer - 304 Not Modified.
What issues does the module help with?
• Traffic economy
• If the page hasn't been changed, then the server will stop the data transfer after it sends heading with 304 Not Modified code. The body of the page, images and other objects will not be transferred.
Server load decrease
When you set up the addon, you can reduce the server load (up to 30% and more). It is particularly useful for the site with high attendance and prolonged user visits.
Acceleration of indexation by search engines
Google with the help of webmasters guidance recommends sending the heading Last-Modified and process If-Modified-Since correctly.
Search engine recommendations
The stated headings are recommended Google search engines.
Here are the links to Google description https://support.google.com/webmasters/answer/35769...
Google description quotes:
"Make sure that your web-server supports HTTP-header If-Modified-Since. With its help, Google figures out whether the site’s content has been changed since the last time it has been scanned. This function helps to reduce the unnecessary server load."
The module has very flexible settings – you can set up the headers for all the key pages of the website, you can choose the headers shown to particular customers or search engines.