Hi, this can be influenced by a particularly long bookmark, but more likely in your case, the location of the bookmarks button can change the way folders open. For example, I have moved the bookmarks button to the left-hand end of the bookmarks bar, so everything opens to the right, simply because there is no space on the left. It's possible therefore, that another button you've added has moved the it to the left - leaving more space on the right, so you could perhaps try dragging it to the right - click on Customize as shown in Customize Firefox controls, buttons and toolbars and you will be able to move it.

If your question is resolved by this or another answer, please take a minute to let us know. Thank you.

Thanks for taking the time to offer a solution but unfortunately it hasn't helped. I have deleted all the new bookmarks added since they started opening on the right - there are no long bookmarks. I have moved the bookmarks button to the left of the toolbar. No difference. I have added more icons as well as the bookmarks button to the left of the toolbar to leave even more space on the right - no difference. This happened before and then for no apparent reason the bookmarks started opening to the left again - as I wanted. I just don't seem to be able to control it and I certainly can't find a way to open on the left as a default.

As I posted above, I just couldn't change it. I thought "O.K., I'm going to have to get used to it." Then this morning when I opened Firefox the bookmarks have reverted back to opening on the left again. So it goes ....

You can open the bookmarks sidebar via "View > Sidebar" to have the bookmarks available all the time in the sidebar.

Thanks again for taking the time to reply, I'm aware of that and isn't what I'm on about. Let me explain clearly - Opening Firefox, on the home page and on the tool bar from left to right - File, Edit, View. History. Bookmarks, Tools, Window, Help. O.K. - Now, click on "Bookmarks" and the menu drops down in the centre of the screen. A list appears and on the left of each listed item is a folder icon and over to the right, an arrow (actually a small triangle pointing right). As I scroll down the items, individual items within each folder, along with any sub-folder, appear to the side of the main drop down menu. Most often to the left, but occasionally, for no apparent reason, they suddenly appear to the right. Question: Is there a way to ALWAYS make them appear on the left? I don't lose sleep over it, just curious. I cannot find any pattern whatsoever that makes it change. Since the last post it has changed again and I haven't added any new bookmarks.

Did you check the names in the folder that open to the right to see if there are long names that require to open to the right (if that is where most space is)?

If it is the opposite then may make one of the names longer to see if that makes Firefox switching sides.

I have been through that - the length of the bookmark names remains unchanged. The switch from left to right is random. The first response to my question was from "Scribe" who suggested a long bookmark name could be the issue. Logical - so I went through every bookmark name, shortening them as much as possible. No change. I was opening bookmarks several times a day, they still continued to open on the right - no change, Then four days later they reverted to the left and I had not amended or added anything. I continued to open bookmarks several times a day without adding a new one or changing anything and today it has reverted to the right again. This is clearly happening without any input from me. It is not a PEBKAC problem ("Problem Exists Between Keyboard And Chair).