You can add or remove icons depending on your needs.Home icon is placed in the navigation bar.Right click the empty strip of navigation bar.From the menu select customize.The customize tool bar window opens.To add an item say home icon drag it from the window to where you want to appear.When finished click done

It is possible that you opened the right-click context menu and clicked the "Remove from Toolbar" item or the "Move to Menu" item. The former moves the toolbar button to the Customize palette and the latter moves the toolbar button to the "3-bar" Firefox menu button drop-down list. You can restore the Home button to the Navigation Toolbar via the Customize mode. If you can't find this button then click Restore Defaults at the bottom of the Customize palette window.