If it is the Bookmarks or History sidebar, you can click the "x" to the right of the word Bookmarks or History at the top of the sidebar, or

• Bookmarks sidebar - CTRL+B opens or closes
• History sidebar - CTRL+H opens or closes

Other - You should check your Plugins and update as needed:

1. Check your Plugins - https://www.mozilla.org/en-US/plugincheck/
2. Adobe Shockwave for Director Netscape plug-in, version 11.5 (not the same as Adobe Flashplayer/Flash/Shockwave Flash)
   • http://kb.mozillazine.org/Shockwave
   • Download, save, close all browsers, run the installer that you just downloaded - http://get.adobe.com/shockwave/

My situation with the sidebar is a bookmarked website opens when I click the name. How do I get rid of it? Thx

Opening in the sidebar is the default for bookmarks that are created via a link or button on a website.
You can check the Properties of a bookmark via the context menu in the sidebar (Ctrl+B; Command+B on Mac).
In the Bookmarks Manager (Bookmarks > Show All Bookmarks) you can click the More button in the Details pane at the bottom right.
Make sure that "Load this bookmark in the sidebar" is not selected.