When you check your website using http header tools you can see that your website is not optimize.
Reason:You find that your website is not optimize and you have check with webpage tester that your website is does not have caching enable.
Solutions:You may force your website to use caching that has been ready by our web server. Please add below script into your .htaccess file:
ExpiresActive On
ExpiresDefault A1800
# 1 Week
<FilesMatch "\.(ico|gif|jpg|jpeg|png|flv|ttf)$">
Header set Cache-Control "max-age=604800"
</FilesMatch>
# 1 Week
<FilesMatch "\.(js|css|pdf|txt|swf)$">
Header set Cache-Control "max-age=604800"
</FilesMatch>
# 1 Hour
<FilesMatch "\.(html|htm|php|php3|)$">
Header set Cache-Control "max-age=3600"
</FilesMatch>
