I've deleted some products but they still show in the content tree. How do I get rid of them?

When you delete an item in the content tree it does not get fully removed from the database straight away so that you can temporarily delete something and re-instate it at a later date or it can be un-deleted if you accidentally delete the wrong thing. To completely remove the items that are marked with a 'red cross' in the content tree, go to the 'Housekeeping' menu and select 'Purge | Purge Content'.

Note that this will delete everything marked with a red cross so if you have temporarily deleted an item you will have to un-delete it before purging. If you regularly, temporarily mark items for deletion, it may be better to just untick the 'Hide on Website' option for those products/sections, so that you can easily purge items that you want to remove permanently.