A browser retrieves many resources from the webserver (css/js, etc). Cache allows websites to store this files in temporary storage to allow faster retrieval next time the file is needed.
mod_expires headers
Using these statements we can inform the browser that it can cache files for a longer period. Make sure mod_headers is enabled in apache.
<IfModule mod_expires.c>
ExpiresActive On
ExpiresByType text/css "access 1 month"
ExpiresByType text/html "access 1 month"
ExpiresByType image/gif "access 1 year"
ExpiresByType image/png "access 1 year"
ExpiresByType image/jpg "access 1 year"
ExpiresByType image/jpeg "access 1 year"
ExpiresByType image/x-icon "access 1 year"
ExpiresByType application/pdf "access 1 month"
ExpiresByType application/javascript "access 1 month"
ExpiresByType text/x-javascript "access 1 month"
ExpiresByType application/x-shockwave-flash "access 1 month"
ExpiresDefault "access 1 month"
</IfModule>
Cache control in mod_headers
<ifModule mod_headers.c>
<filesMatch "\.(ico|jpe?g|png|gif|swf)$">
Header set Cache-Control "public"
</filesMatch>
<filesMatch "\.(css)$">
Header set Cache-Control "public"
</filesMatch>
<filesMatch "\.(js)$">
Header set Cache-Control "private"
</filesMatch>
<filesMatch "\.(x?html?|php)$">
Header set Cache-Control "private, must-revalidate"
</filesMatch>
</ifModule>
Turn off ETags
By removing the ETag header, you disable caches and browsers from being able to validate files, so they are forced to rely on your Cache-Control and Expires header.
<IfModule mod_headers.c>
Header unset Etag
Header set Connection keep-alive
</IfModule>
FileETag None
Deflating compression
Compression is implemented by the DEFLATE filter. The following directive will enable compression for documents in the container where it is placed; again, make sure the module is enabled in Apache.
<IfModule mod_deflate.c>
# Compress HTML, CSS, JavaScript, Text, XML and fonts
AddOutputFilterByType DEFLATE application/javascript
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/vnd.ms-fontobject
AddOutputFilterByType DEFLATE application/x-font
AddOutputFilterByType DEFLATE application/x-font-opentype
AddOutputFilterByType DEFLATE application/x-font-otf
AddOutputFilterByType DEFLATE application/x-font-truetype
AddOutputFilterByType DEFLATE application/x-font-ttf
AddOutputFilterByType DEFLATE application/x-javascript
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE font/opentype
AddOutputFilterByType DEFLATE font/otf
AddOutputFilterByType DEFLATE font/ttf
AddOutputFilterByType DEFLATE image/svg+xml
AddOutputFilterByType DEFLATE image/x-icon
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE text/html
AddOutputFilterByType DEFLATE text/javascript
AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/xml
# Remove browser bugs (only needed for really old browsers)
BrowserMatch ^Mozilla/4 gzip-only-text/html
BrowserMatch ^Mozilla/4\.0[678] no-gzip
BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
Header append Vary User-Agent
</IfModule>