Unfortunately the browser cache is stored internally and not on the SD card. I have no idea what the internal memory size is, but it's not that big.
So your phone won't handle full web pages... you need to locate mobile versions.
for msn.com it's: mobile.msn.com
For a list of some sites, go to http://cantoni.mobi/
Unfortunately, this site won't load on the P168 either. You have to manually enter the pages you use as bookmarks.