Milan Dinić

Gzip

After looking to pgcache folder and .htaccess, my understanding is following:

• for every page, both static html file is made and it’s gzipped (precompressed) version
• if browser supports gzip, gziped version is sent

This is because sending precompressed version uses less server resources then gziping on the fly?

Is above true?

If it is, does this conflicts with use of mod_deflate? For example, by default, in site’s root .htaccess file I add:

<IfModule mod_deflate.c>
AddOutputFilterByType DEFLATE text/html text/plain text/xml text/css application/javascript application/x-javascript application/x-httpd-php application/rss+xml application/atom_xml
</IfModule>

If precompressed version is sent and there is this in .htaccess, will content be compressed again or Apache knows that it is already compressed and does nothing? Note that this stays in .htaccess below W3TC’s lines which are at top.

What is difference between types of compression (gzip, deflate, gzip and deflate)? How their use have effect on server’s load and to visitor’s computer (since content needs to be decompressed and different levels of compressions requires different power and time to decompress)?

(note that this sections applies to minifying of CSS and JS too)

Minify

It seems that minifying is used even when caching of page is not used. There is option to turn off minification for administrators, but what about other logged-in users, commenters, pages excluded from caching and every other situation where minification is done on every page load?

I am asking this because HTML minification is very expensive in terms of server resources.

Adding CSS and JS files

Should files be added by copying whole URL (eg. http://example.net/wp-includes/js/jquery/jquery.js?ver=1.3.2) and are they after that removed only while they are with exact URL, or are they deregistered from WP (eg. what will happen when jQuery in WP is upgraded to 1.4.2: will that new script be minified and removed or only old one because of different URL)?

What do groups mean? Are those files we add minified only for that group or what?

What does non-blocking means for JS?

What happens when already minified JS file is added: will it be tried to be minified again or script will recognise minification?

Cache and headers

Sections for expiration of cache and use of cache control headers are not explained. Questions are:

• If we turn on cache control headers, where to setup max age of cache?
• What is difference between “Maximum lifetime of cache objects” and “Garbage collection interval”? When someone looks at it, he can conclude that both things are related to how often W3TC regenerates caches of pages.
• To what external files “Update external files every” applies?

(note that this sections applies to page cache and CSS and JS too)

Page Cache

When pages that shouldn’t be cached are added, should we add them like http://example.net/page, /page or simply page?

Regeneration of cache

I read that cache is regenerated when new entry or edit was made but what if something else is updated, like RSS widget, Twitter etc?