These are pretty standard settings, simply lines entered in your site’s root .htaccess file.  Be careful modifying your .htaccess file, if you don’t know what you’re doing a rogue semi-colon (;) could easily take your site down and throw that dreaded “500 Server Error” — that’s not the kind of error you want your website to get, but even though a 500 error looks bad, it’s amazing how you can bring a site down so easily with a simple character or a single line of code in many types of scripts.

An “.htaccess” file isn’t really a script, though it can contain behaviors and conditions, it’s more a set of directives that let the server know what you want it to do and how it can act.  Since it’s so powerful and does so much, with great power comes even greater responsibility. Keep in mind that you should be testing these directives on a “dev” server (development server) and not your live site!  Also these lines are generally accepted, but your flavor of Linux might require a different approach or modifying the settings and commands to work properly on your particular server.

<ifModule mod_gzip.c>
mod_gzip_on Yes
mod_gzip_dechunk Yes
mod_gzip_item_include file \.(html?|txt|css|js|php|pl)$
mod_gzip_item_include handler ^cgi-script$
mod_gzip_item_include mime ^text/.*
mod_gzip_item_include mime ^application/x-javascript.*
mod_gzip_item_exclude mime ^image/.*
mod_gzip_item_exclude rspheader ^Content-Encoding:.*gzip.*

<ifmodule mod_deflate.c>
AddOutputFilterByType DEFLATE text/text text/html text/plain text/xml text/css application/x-javascript application/javascript text/javascript
#End Gzip

# More optimizing

# BEGIN Expire headers
<ifModule mod_expires.c>
ExpiresActive On
ExpiresDefault "access plus 5 seconds"
ExpiresByType image/x-icon "access plus 2592000 seconds"
ExpiresByType image/jpeg "access plus 2592000 seconds"
ExpiresByType image/png "access plus 2592000 seconds"
ExpiresByType image/gif "access plus 2592000 seconds"
ExpiresByType application/x-shockwave-flash "access plus 2592000 seconds"
ExpiresByType text/css "access plus 604800 seconds"
ExpiresByType text/javascript "access plus 216000 seconds"
ExpiresByType application/javascript "access plus 216000 seconds"
ExpiresByType application/x-javascript "access plus 216000 seconds"
ExpiresByType text/html "access plus 600 seconds"
ExpiresByType application/xhtml+xml "access plus 600 seconds"
# END Expire headers

# BEGIN Cache-Control Headers
<ifModule mod_headers.c>
<filesMatch "\.(ico|jpe?g|png|gif|swf)$">
Header set Cache-Control "public"
<filesMatch "\.(css)$">
Header set Cache-Control "public"
<filesMatch "\.(js)$">
Header set Cache-Control "private"
<filesMatch "\.(x?html?|php)$">
Header set Cache-Control "private, must-revalidate"
# END Cache-Control Headers