commandButton mouseover hits server, need cache

[dave_n]

primefaces-3.0.M2-SNAPSHOT
IE8
Default theme
Faces Servlet url-pattern = *.jsf

For every mouse-over the commandButton hits the server. For example:
GET /prodlog/javax.faces.resource/themes/sam/images/ui-icons_454545_256x240.png.jsf, contentlength: -1

Isn't there a way to cache these and not run back to the server each time?