This page gives an overview of which page types are used by other extensions already. Although the page type (typeNum) is configurable, it is advisable to choose a type that is not used by any other extension yet.
NOTE: some of these typeNums might get obsolete with TYPO3 4.0 where extensions can hook [deprecated wiki link] up into index.php and take over the rendering of the page via the eID HTTP GET parameter. But for backwards compatibility we should try to stick with these reserved typeNums.
100-110 for various XML export formats like RSS, RDF or ATOM. Actually only 100 is used by default, but users can configure additional XML formats or different feeds for different categories and thus it is needed to keep at least a range of 10 page types free.
157 for indicating that the page is of type customer
200 for XML-RPC Server, might get opened for other extensions using XML-RPC if the Server component gets moved into an own extension
500 for Ajax [deprecated wiki link] communication
761 for XML-RPC service
1000 for XML feed service
2008 for web feeds in Atom format
9009 for podcast XML
201 for Category Pages
99 for plaintext version of the newsletter
199 for plaintext preview of the newsletter
157 for file pages. this value is configurable.
181 for "Cart: Cart"
182 for "Cart: Product"
183-185 for some planned features