Unfortunately, Safari doesn't yet allow the user to manually adjust the size of the cache nor select an option to refresh the page on each visit. For most Internet browsing, refreshing page content hasn't been an issue for me: it seems that even on pages that change constantly I get the new content when I navigate to them.
I only start having real trouble when checking the webpages I create (when making one change after another and viewing code-to-page) on the local machine. When I'm not seeing my changes (like, after ten or so reloads) here is what I do:
Select Empty Cache from the Safari menu (I started typing something else before and went and edited this, see reason for editing...sorry), click OK, and then click the Refresh button on the toolbar (a partial circle with an arrow.) In most cases, this clears the problem right up and shows the refreshed content.
In others, you may need to do the above, plus Quit Safari and then restart it. In any case you should clear your cache and unwanted cookies daily. I like being able to manually pick and choose the cookies I keep and toss.
(yes, pun intended).
I'm running OS 10.3.9 and Safari 1.3.1, so I am not sure if the above applies to Tiger and Tiger apps.
The Apple website has a great peer-to-peer message board for support issues---someone there might have a better trick.
good luck!
terry