I got F's (bad) in Yahoo's YSlow for "Add Expires headers" and "Compress components with gzip." How do I fix them? I tried adding the following to my .htaccess file, but it didn't work.

Code:
# Expire images header
ExpiresActive On
ExpiresDefault A86400
ExpiresByType image/gif A31104000
ExpiresByType image/png A31104000
ExpiresByType image/jpg A31104000
ExpiresByType image/jpeg A31104000
ExpiresByType image/ico A2592000
ExpiresByType text/css A86400
ExpiresByType text/javascript A86400


# compress text, html, javascript, css, xml:
AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/html
AddOutputFilterByType DEFLATE text/xml
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/javascript
AddOutputFilterByType DEFLATE application/x-javascript