Optimering efter firfox plugin "firebug"

Jeg har prøvet at lade "firebug" ko0mme med foreslagf til forbedringer.
Og der kom en temmelig lang liste, så jeg starter liger med nogler af de første.

Som i kan se her under skriver den "expiration not specified" men hvordan pokker gør jeg det, altså sætter expiration for et billedede? eller for et .css? Jeg ved det virkelig ikke.
Håber nogen kan/vil hjælpe

   
(!)Leverage browser caching
The following cacheable resources have a short freshness lifetime. Specify an expiration at least one week in the future for the following resources:

    * http://lachica.dk/admin/Forsideny/assets/201031.forside.4.aug_5539.jpg (expiration not specified)
    * http://lachica.dk/css/default.css (expiration not specified)
    * http://lachica.dk/favicon.ico (expiration not specified)
    * http://lachica.dk/img/ikoner/info.png (expiration not specified)
    * http://lachica.dk/img/search.gif (expiration not specified)
    * http://lachica.dk/img_BetalKort/betalingskort.gif (expiration not specified)
    * http://lachica.dk/logoer/amust.jpg (expiration not specified)
    * http://lachica.dk/logoer/bananamoon.jpg (expiration not specified)
    * http://lachica.dk/logoer/bjorn_borg.gif (expiration not specified)
    * http://lachica.dk/logoer/blend.jpg (expiration not specified)
    * http://lachica.dk/logoer/customized.jpg (expiration not specified)
    * http://lachica.dk/logoer/defeeter.jpg (expiration not specified)
    * http://lachica.dk/logoer/dg.jpg (expiration not specified)
    * http://lachica.dk/logoer/didriksons.jpg (expiration not specified)
    * http://lachica.dk/logoer/dixie.jpg (expiration not specified)
    * http://lachica.dk/logoer/dunlop.jpg (expiration not specified)
    * http://lachica.dk/logoer/forrestbob.jpg (expiration not specified)
    * http://lachica.dk/logoer/friisco.jpg (expiration not specified)
    * http://lachica.dk/logoer/globalfunk.jpg (expiration not specified)
    * http://lachica.dk/logoer/gstar.png (expiration not specified)
    * http://lachica.dk/logoer/hotmakeup.jpg (expiration not specified)
    * http://lachica.dk/logoer/justfemale.jpg (expiration not specified)
    * http://lachica.dk/logoer/killah.jpg (expiration not specified)
    * http://lachica.dk/logoer/mbym.jpg (expiration not specified)
    * http://lachica.dk/logoer/myfavourites.jpg (expiration not specified)
    * http://lachica.dk/logoer/numph.jpg (expiration not specified)
    * http://lachica.dk/logoer/papfar.jpg (expiration not specified)
    * http://lachica.dk/logoer/partyline.jpg (expiration not specified)
    * http://lachica.dk/logoer/rutme.png (expiration not specified)
    * http://lachica.dk/logoer/samsoe.gif (expiration not specified)
    * http://lachica.dk/logoer/sbar.jpg (expiration not specified)
    * http://lachica.dk/logoer/second_female.gif (expiration not specified)
    * http://lachica.dk/logoer/selectf.jpg (expiration not specified)
    * http://lachica.dk/logoer/senze.jpg (expiration not specified)
    * http://lachica.dk/logoer/sistersp.jpg (expiration not specified)
    * http://lachica.dk/logoer/soft.jpg (expiration not specified)
    * http://lachica.dk/logoer/stoej.jpg (expiration not specified)
    * http://lachica.dk/script.js (expiration not specified)
    * http://lachica.dk/varer_pic/thumbnails/13092010101900.jpg (expiration not specified)
    * http://lachica.dk/varer_pic/thumbnails/13092010115706.jpg (expiration not specified)
    * http://lachica.eu/kategori_pic/logo.jpg (expiration not specified)
    * http://www.google-analytics.com/ga.js (1 day)