Here's our tutorial with video on How to Delete Bookmarks on iMac (Safari, Google Chrome and Firefox).
Safari:
Hold down the "Control" key on your keyboard and then left click on all the bookmarks that you want to remove. Once you have done this you need to press the "Delete" key on your keyboard. Right clicking and pressing "Delete" will not work for removing multiple bookmarks at once in Safari.
Google Chrome:
In Google Chrome just go to Bookmark then Bookmark Manager then right-click the bookmarks you wanted to remove then press Delete.
Firefox:
In Firefox just go to Bookmark then Show All Bookmarks then right-click the bookmarks you wanted to remove then press Delete.