Why you should get this: It gives you more control over what you surf. Don't like ads popping up all over the page? Easily done. Without all the scripts running in the background, your web pages load faster and you can surf safer too. Need to view the page with everything turned on? Just hit the 'temporarily allow all scripts' option and the page runs as per normal. This add-on is also frequently updated for added security.
Issues: Apart from having your webpages occasionally looking messed up and perhaps looking too bare, we don't really see any other detrimental side effects using this add-on.
Plug-in Availability: Get NoScript here.
WOT - Web of Trust
In a nutshell: If you need to go one step further because you're really paranoid about what you surf, then the WOT (Web of Trust) add-on will really soothe you. What it does is simply to provide you with community based ranking system of over 21 million websites, so when you visit a site - you'll be able to know how safe or reliable the site is. You can also help sites that you often visit by ranking them and sharing the love.
Why you should get this: If NoScript isn't safe enough for you, then this is something you should try. If you're worried about your kids visiting unsafe websites - the add-on also works as a site filter to block out undesirable sites. As mentioned, you get to view the feedback from the other users, while also adding your own feedback, making it a pretty reliable tool for surfing the Internet.
Issues: You may encounter issues with a website getting a wrong rating, but this is usually rare. Also if you already have an anti-virus program that does the same thing, there's really no need to get this, unless you're really extremely paranoid.
Plug-in Availability: Get Web of Trust here.
In a nutshell: Hate seeing ads all over the webpages you visit? Then this add-on is the one for you. It blocks off almost every ad possible and does so with minimal set up. There's no need to configure anything apart from subscribing to a list (which provides the add-on with all the data of the advertisements' web addresses). And if you stumble upon a website that isn't blocked in the list, well, you can still manually block them yourself.
Why you should get this: If you've no desire to mess around with the NoScript add-on, this works very well on its own and blocks off most of the annoying ads online. Ads before videos are also blocked, so you can watch flash videos online with no commercial interruptions. As an added bonus, because it blocks off ads before it loads - you're effectively saving bandwidth and website loading time.
On a side note, this add-on also works well with the NoScript and Remove it Permanently add-ons (seen on the next page).
Issues: Well, you're missing out on ads of course! There are plenty of genuinely good ads that may interest you from deals to services. Contrary to what some staunch net users think of relying on community, you probably might miss out on a good offer or product you might have been looking for due to reliance of second-hand information from the community who in turn rely on advertisements or by further word-of-mouth.
Plug-in Availability: Get AdBlock Plus here.