Well, usually when we visit different sites we face many ads and some of them are flash based, some Java based and some just text based. Flash based ads use great bandwidth and also contain many security holes in them, so they are not secure and pretty dangerous for you PC, similar thing is with Java based ad (used in youtube videos). Text based ads are not that much dangerous but they some type distract you. Why Ads are so much problem, these are not unless they just pop-up in new window, which is so annoying? Sometime these ads contain disgusting and vulgar material on them. Google Adsense is Text based type.
Simple method is modifying HOST file present in your Windows and Linux distro, well this is nice method but it leaves annoying places with Page cannot displayed on website. NO, I am going to tell you plugins and some software which can you install and get rid of them.
For Internet Explorer:
Well, there is nice software so called addon for this purpose namely, IE7 Pro. It is comfortable with Internet Explorer 6, 7 and Internet Explorer 8 (it is pointless to use IE6, so I recommend you to download IE8). It has also Ad Block feature.
By selecting them you can get rid of your ADS, this so simple, I think you can get it now.
Firefox is good for its approachable addons, it has feature enhanced features. The best addon for ADS blocking is AD Block Plus, by using Easylist, you can get rid of your ads, it is best and mine favorite one because it blocks Flash based, JAVA based and Text Based Ads.
For Google Chrome:
Chrome has also wide range of addons but it for its own security reasons, Chrome did not allow so much features to addons, it put limits on it, I searched many but I personally used this AdBlock+ Element Hiding Helper with little bit modification, I just change Subscription to Easylist of Firefox. For modification, put this url
it does not block JAVA based ads. Chrome user well aware with this setting location.