Thank you, but in that case I'm not sure I understand the purpose of Library Items. Before I added the Library Item, there was nothing to preload. When I add a rollover to the Library Item, Dreamweaver creates the preloader instruction within the Library Item. Then when I include the Library Item in an html page, Dreamweaver controls where the preloader is put.
Do I then need to manually edit what Dreamweaver has done? In this instance it would have been almost as quick to have ignored the use of a Library Item and copied and pasted the relevant code into the two pages and manually created the revised <body> tag with a preloader. In my relative inexperience with Dreamweaver, I just thought that using a Library Item in multiple pages would save me some effort when I wanted to change the content of the Library Item. As I said, the Library Item worked OK until I added a rollover within it.
I never use Library Items because they certainly do have limitations. IMO, Server-Side Includes or code Snippets are much more flexible options for re-usable content.