Using Permalinks « WordPress Codex: "a "pretty" permalink structure, WordPress will generate rewrite rules and attempt to insert them into the proper .htaccess file. If it can't, it will say something like You should update your .htaccess now and print out the rules for you to copy and paste into the file (put them at the end).
In WordPress 2.0+ versions, you'll probably need to do this only once, because WordPress does the rewriting internally. If you ever move your WordPress home directory (Site address), you'll need to repeat this step.
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