First, thanks to everyone who replied to my previous questions. In particular, the first person to reply was Richard Sullivan. I thought I had replied to him, but I can't find it.
I'm still left with two problems. The minor one is that on each page except the home page, below the line containing links to all the pages, there's a line containing "Home" and "Contact" (which is the name of another page). "Home" actually works as another link to the home page, but "Contact" is greyed out and does nothing. This line seems entirely unnecessary.
The major problem concerns the home page, where the text in "Body text" doesn't appear. This may be because the Layout tab shows no active includelets - I think "Contact item" should be there. It is there under "Scratch", but the system doesn't allow me to drag it back. Also, the "Add includelets" line no longer appears. I think it used to appear or not at random, but now it's given up completely.
Not sure if you have already solved the problem with your home page not displaying the body text, but if not then it is almost certainly what you suspect - the 'content item' includelet needs to be in the 'content' column of the layout tab.
There are a couple of reasons that may prevent you from dragging it there.
Firstly, if the includelets on the layout tab are grey and there is a message, "The latest revision of this item is published." in a yellow area at the top of the tab, then click the "Create a new revision to make changes." link. This will put the page into edit and allow you to drag the includelets from column to column.
Secondly, the system can sometimes be a little fussy about the exact spot to drag includelets to. The best approach is to drag the includelet and when it is over the column that you want to drop it into, watch for a thin horizontal red line to appear in the column. When that appears you can safely drop the includelet and it should appear at the position of the red line. If the line doesn't appear immediately, moving slightly further down the column will usually get it to show up.
Once you have moved the includelet, go to the 'edit' tab and click the 'save and publish' button to make the change live on your site.
The second issue (the line containing "Home" and "Contact" beneath your navigation menu): without seeing your site, my best guess would be that this is the breadcrumb ( or crumbtrail).
The breadcrumb provides links to the pages between the current page and the site's homepage – essentially it's a way of indicating to people where they currently are in your site.
For example, if your site was about food, it might have a section on recipes, and that might be divided into recipes for meat, fish and vegetables. If there was a page for a Lancashire hotpot in the meat section then its breadcrumb may be something like this:
Home > Recipes > Meat > Lancashire hotpot
And everything in the breadcrumb except Lancashire hotpot would be a link leading to a page.
On a small site with only a few pages, the breadcrumb won't provide much benefit (for most pages the breadcrumb may only show the name of the current page and the link to Home), but equally it won't cause any harm. On a more complex site, like the example above, it can help people know which part of the site they are in and provide a quick way to navigate.
I think in another post, you said that your site uses the Modern theme. There isn't a simple way to hide the breadcrumb in Modern, so I'd be inclined to leave it as is. If you really want to hide the breadcrumb, reply here and I can outline the options for you.
Thanks for both your answers John. About moving includelets, I did eventually work out for myself why I couldn't move them.
About the breadcrumb trail, I don't think it's necessary at present, but it's possible that the website will grow into a more complicated structure, and then it will be useful. So I think I'll leave it as it is, but if you want something to pass the time, you could write something here about it, and it may be useful to other people.
Incidentally, the second item in the breadcrumb trail shows as "Content" in Preview, but as the name of the current page when I look at the actual website. So much for WYSIWYG.