offline compression in Apache

.htaccess

AddType text/html       .html_gz
AddType text/javascript .js_gz
AddType text/css        .css_gz

AddEncoding gzip .html_gz .css_gz .js_gz

IndexIgnore *_gz

RewriteCond %{HTTP:Accept-Encoding} gzip
RewriteCond %{REQUEST_FILENAME}_gz -f
RewriteRule ^(.+)\.(html|css|js)$ $1.$2_gz [E=no-gzip:1]
Header merge Vary "Accept-Encoding"

compress.sh

for f in $(find . -name '*.html' -or -name '*.css' -or -name '*.js') ; do
  gzip -nc9 $f > ${f}_gz
done