That is the intended behaviour. Sorting in the Library is intended just to display the bookmarks in a different order but not save the order.

For more details see Sorting and rearranging bookmarks - MozillaZine Knowledge Base

The SortPlaces add-on may be of use to you, it gives you more control over sorting bookmarks.

In other words your saying the Library's structure is outside our control in Firefix without 2nd party add-ons? Sounds like something that I've come to expect from Bill's outfit. (MS) Anyway, thanks for the response.I will give the recommended add-on a test run. Score to date: User satisfaction Firefox 3.6+ stands at -3.

You can right-click a folder (but not an individual bookmark) in the Library or sidebar to sort the bookmarks in that folder as explained in the above mentioned article.