Web Design Rookie Has a Few Questions

[AspiringWebDesigner]

I downloaded the firefox extensions YSlow and I have a few questions about how to implement it's recommendations.

 

#1 GZip. How do I implement GZip into my website? The helps section (http://developer.yahoo.com/performance/rules.html#gzip) makes it look like I only have to add a few lines.

 

#2 YSlow says, "There are 2 static components that are not on CDN." I read the help section, but I still don't understand what CDNs are. Would an example of a cdn be, godaddy.com?

 

#3 YSlow says to add expire headers. "There are 2 static components without a far-future expiration date." Is this important and if so...how would I do this?

 

Thank you,

 

Andre

[shelfimage]

Here's what I use in my htaccess file to help gzip compression, headers, etc. But first, Compression can be enabled on your server within the PHP settings (php.ini) if you are on a shared hosting server, then you *might* be able to create a custom php.ini file for your account - ask your web host what they support and how to change default PHP settings. Example, the php.ini file will need:

zlib.output_compression = On
zlib.output_compression_level = -1

 

Example .htaccess rules for compression and expires:

 

# ##### Performance Rules ##### #


       BrowserMatch ^MSIE [6-9] gzip
       BrowserMatch ^Mozilla/[5-9] gzip
       AddOutputFilterByType DEFLATE text/html text/css text/javascript application/x-javascript
       Header append Vary User-Agent



# Expires
ExpiresActive On
ExpiresDefault A0

# 3 months - media files

ExpiresDefault A7257600
Header append Cache-Control "public"
Header unset ETag
Header unset Last-Modified
FileETag None


# 1 month - image files

ExpiresDefault A1209600
Header append Cache-Control "public"
Header unset ETag
Header unset Last-Modified
FileETag None


# 3 days - text based

ExpiresDefault A259200
Header append Cache-Control "public, proxy-revalidate"
Header unset ETag
Header unset Last-Modified
FileETag None


# 5 minutes - dynamic

Header set Cache-Control "max-age=300, private, proxy-revalidate"


# Force no caching for scripting

ExpiresActive Off
Header set Cache-Control "private, no-cache, no-store, proxy-revalidate, no-transform"
Header set Pragma "no-cache"
Header unset Last-Modified

 

CDN - Content Delivery - simply put, large sites will use alternate servers (usually in several locations) to serve media and content for their website. So, not everything is on one server. You can trick Firebug by added the site's domain name you are testing to the CDN hostname setting. See: http://developer.yahoo.com/yslow/faq.html#faq_cdn