extend_cache - makes sure that everything is cached, make sure that your scripts do not do something like
btn.style.backgroundImage = 'hover.png'
before
after
- avoid it if your JavaScript uses HTML comments
before
after
elide_attributes - removes unnesessary attributes, avoid it if your styles contains something like
input[disabled="disabled"] {...}
before
after
inline_css - inlines small stylesheets, less than ModPagespeedCssFlattenMaxBytes, which is 2kb by default, can be configured in
/etc/apache2/mods-enabled/pagespeed.conf
before
after