If you find your monitor or notebook screen has a lot of glare from external light sources when using it, you should invest in either an Anti-Glare Screen or Privacy Filter. Glare can lead to headaches and eye strain. Use this guide to help choose the right screen or filter for your needs:
Anti-Glare screens will generally block from 90-99% of glare from external light sources. They also have anti-radiation and anti-static properties, although this is only good for CRT monitors as LCD's have very little radiation and are anti-static by nature.
They will also help to protect your screen from fingerprints and scratches. Anti-glare screens use hangers to attach to the monitor, but check to see that they have the correct hanger for your monitor as the CRT and LCD hangers are different. Also be sure to choose a glare screen that is the right size for your monitor.
Privacy filters darken the screen when viewed from the side keeping your on-screen data private. There is no blurring or image distortion. They are also similar to an anti-glare screen as they reduce screen glare by up to 95%, and also have anti-radiation, and anti-static properties.
If you constantly have to collaborate your work with others then they can become bothersome, as you will have to constantly take the Privacy Filter off or they will not be able to see your screen. Privacy filters can attach to the monitor or notebook via hangers or stick-on tabs (which you then slide your privacy filter into). Check to see that the Privacy Filter will fit the screen size as sometimes they may have the same measurements, but one may be designed for widescreen monitors (e.g. 14.1" and 14.1" widescreen).