Apache 2 can compress text content before sending it. This gives a real speed boost, even for people with fast connection speeds. Compression is carried out by the Deflate Module.

The default settings for mod_deflate don't quite cut it with Internet Explorer. IE likes to tell web servers it's capable of doing things that it isn't.

Some additional directives need to be added to the configuration to make sure that only things IE can genuinely handle compressing are compressed.

There are also a lot of extra content types that can be compressed, which are listed in the default config. Likewise, there are plenty more files types that should never be compressed at all.

LoadModule deflate_module modules/mod_deflate.so

# Insert filter
AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/xml
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE image/svg+xml
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/atom_xml
AddOutputFilterByType DEFLATE application/x-javascript
AddOutputFilterByType DEFLATE application/x-httpd-php
AddOutputFilterByType DEFLATE application/javascript
AddOutputFilterByType DEFLATE text/html
AddOutputFilterByType DEFLATE text/javascript

# Netscape 4.x has some problems...
BrowserMatch ^Mozilla/4 gzip-only-text/html

# Netscape 4.06-4.08 have some more problems
BrowserMatch ^Mozilla/4\.0[678] no-gzip 

# MSIE masquerades as Netscape, but it is fine
# Don't deflate content for IE by default - only deflate text/html content
BrowserMatch \bMSIE no-gzip !gzip-only-text/html msie
BrowserMatch \bMSIE\s6 msie6
BrowserMatch \bMSIE\s7 !no-gzip !gzip-only-text/html msie7
BrowserMatch \bMSIE\s8 !no-gzip !gzip-only-text/html msie8

# Don't compress images etc
SetEnvIfNoCase Request_URI \
\.(?:gif|jpe?g|png|zip|tgz|gz|bz|pdf|exe|doc|xls|bin|bmp|ico)$ no-gzip dont-vary

# Make sure proxies don't deliver the wrong content
Header append Vary User-Agent env=!dont-vary