From MozillaZine Knowledge Base
Adblock Plus is an improved version of Adblock with a better user interface, and interfaces better to filter subscriptions so that your own filters and multiple subscriptions will not interfere with one another. Adblock Plus: Element Hiding Helper is a companion extension for Adblock Plus designed to make creating element hiding rules easier and is invoked from the Adblock Plus button's context menu.
Hosts File is a file not an extension, it blocks ads, banners, 3rd party Cookies, 3rd party page counters, web bugs, and even most hijackers. The hosts file contains the mappings of IP addresses to host names. This file is loaded into memory (cache) at system startup, then the system (Windows/Linux) checks the Hosts file before it queries any DNS servers; and, bad domains are blocked and will not be seen. Hosts file blocks some things that cannot be blocked by extensions. A hosts file provides cross-application protection, regardless of what Firefox profile is used or what browser is used, or other applications accessing the web. It should be considered as a primary protection against malware and prevalent major annoyances, but usage is not very flexible as it relates only to a host domain. Adblock Plus provides more flexible filtering to deal better with annoyances than it does with malware, Both types should be used along with Anti-Virus protection.
Eliminate ads. Ads, particularly third party ads, are a primary source of malware and viruses. Eliminating ads helps protect your system, speeds up downloads, and helps protect your system. (video overview). Filters are required -- "EasyList USA" subscription is recommended to start with -- additional subscriptions and your own filters can be added as well. Features: Easy to add customized filter and whitelist items with help from menus and by manually creating your own filters.
Adblock Plus filtering
If you have the "Adblock Plus" extension, you also need to install filters -- without filters, the extension will do nothing. After installing the extension go to the extensions options or right click on the ABP icon, then choose "Preferences" then choose "Add filter subscription" -- the "EasyList USA" is the most widely used and needed filter subscription.
Right click on the ABP toolbar icon or addons bar icon and choose "Open blockable items". Suggest displaying: Address, Filter, Type, and State (sorted, red at top) -- selected from the icon at the right of the titles. From here you can right click on an item and are offered several choices to create a filter that would block that item. You should be familiar with the Getting started usage documentation from when you installed the extension.
If something is blocked you will be able to see what filter blocked it and where that filter resides by hovering over the blocked item line to identify where the filter came from -- which filter subscription(s), or your own. There is also a context (right-click) menu associated with each line. You can block/unblock the filter on that list via the context menu for the line and see the change in the "State" symbol, or permanently delete the filter altogether on the Preferences list.
You can turn ABP off without uninstalling it and without restarting Firefox by right clicking on the ABP icon and choosing "Disable everywhere" and the icon will turn to gray, don't forget to turn filtering back on afterwards to see the icon active with normal red color. Fix your filters though so they work for you, because turning off ABP to run something means you have removed protection.
All of the filters are listed in Preferences . The Preferences list shows filters by location (subscription) and has checkmark boxes to activate or suppress the individual filters, as well as being able to activate or suppress an entire filter subscription. When an entire subscription is suppressed everything within the subscription is grayed over and checkmark boxes disappear within the subscription, when reactivated the status of individual filters is restored to the previous state.
A companion extension "Element Hiding Helper for Adblock Plus" can be installed to remove remaining text area ads. The extension creates filtering to help you block out areas of a page through an interactive interface, be careful with this one as it is very easy to block too much.