You are not obliged to accept cookies and may modify your browser so that it will not accept them. The browser you use not only allows you to see the cookies saved on your computer, but also to control their use. You can control them by allowing them, deleting them individually, or deleting all of them. You can also set your browser to not accept cookies altogether. Do bear in mind that if the latter option is selected, many websites will not function properly, or at all.
It may be possible to set your browser to not accept cookies by default, instead asking for your consent before each cookie is set on your device. This gives you complete control over how cookies operate on your device. However, this does have the drawback of slowing down your browsing experience.
There are different levels of control, too. You are able to prevent just third-party cookies being deployed (such as those from advertising services), and some browsers or optional plug-ins even allow you to block specific companies from whom you do not wish to deploy a cookie, instead of selecting all companies. Please refer to your device's web browser or plug-in guide for details:
To opt out of being tracked by Google Analytics across all websites, visit http://tools.google.com/dlpage/gaoptout, where you can download a Google add-on blocking all tracking cookies.