Firefox 3 and later: (multiple selection) You can select multiple entries without invoking the bookmark for dragging, copying, moving or deleting, (similar to how you can select multiple browsing history items) with use of the Ctrl/Cmd key (to add to a selection) & Shift key (to extend a selection) by clicking to the left of the favicon (webpage icon) in the list to make selection(s). To extend from the last selection made of dis-contiguous entries use Cntr/Cmd+Shift+click. Makes moving several bookmarks from different places to a new location easier. Multiple selection is not available in the drop-down menus, and in Firefox 3 only is not available in left pane of Library List. (Bug 440119)

Once you've selected one or many bookmarks you can use the "Del" key to remove the selected bookmarks.

That's very interesting,I've always thought that the bookmarks library needs more tools to easily organize bookmarks,however:having said that,the trick you illustrated above doesn't work for me,clicking anywhere in the library or sidebar always invokes a single bookmark,no way to select multiple bookmarks either with Ctrl or Shift or Ctrl+Shift,not even in safemode (I've just tried it to determine if some addon was interfering),does this actually work with any 3> Firefox version ? Can you please explain the procedure in greater detail,in case I've missed something?

Can you use Shift + cursor Down key to select more bookmarks?

You should be able to select more items by first left-clicking one and then use Shift + left-click to select all bookmarks in that range. In the sidebar you need to click to the left of the bookmark icon to avoid opening it.

Thanks,that works:a bit tricky to get right (not so much user-friendly,a right click context menu,with the ability to make selections dragging the mouse, wouldn't hurt here IMHO),but Shift + cursor Down key makes multiple bookmarks selection possible.

Bookmarks sidebar -- Multiple selection: To select the first item in the bookmarks sidebar without invoking it, you must click to the left of the favicon (and to the left of the expand indicator in the case of folders). To add another item again select in the same manner but with Ctrl+click.

To extend a selection from the last selected item hold the Shift key and you can click anywhere on the item's row to extent to there,

Library List (both Bookmarks and History) Since it take a double click to invoke the bookmark or history page, it doesn't matter where you click on the line item it only selects it.

If that fails, which you seem to have indicated that it does...

then it would seem that you have installed some extension to make it so that you do not have to double-click in the library list. What extensions do you have with "Bookmark" and/or "click" in their name?

Would you try the above instructions while in "Safe Mode".

In current versions of Firefox, Thunderbird, and SeaMonkey 2, you can restart in Safe Mode via "Help ("Alt+H") -> Restart with Add-ons disabled...". A Safe Mode options window will appear when they restart.

Do not make any changes to the options, just click the "Continue in Safe Mode" button. Clicking on anything else would cause permanent changes (damage).

In Safe mode your extensions are temporarily disabled and will be active again on the next restart.

Actually,it works:it's just very tricky IMHO, as I at first understood you could just click & drag with the mouse,indeed you have to be quite involved with Ctrl and\or Shift *and* the mouse to handle this kind of selection,it works but it's definitely not user-friendly in my book.So much so that,before seeing this thread,I used to believe it just couldn't be done.