When the World Wide Web was in its early days, web pages were static. A user would request a page, and the web server would return a document with text, and maybe a picture or two. By contrast, web pages today employ much more complex code (scripting), providing dynamic and interactive content. While scripting makes web pages more useful, it also introduces the potential for security risks, as anyone can run code on your computer through your web browser. The majority of malware infections occur through web pages loading malicious code through scripts in a web browser.
NoScript is a browser add-on for the Firefox web browser that blocks scripting on web sites until you explicitly allow it on a per-site basis. The nice thing about NoScript is that it will prevent scripts from running by default as you go from page to page on the Internet (such as when you are doing research).
If you encounter a web site that does not quite display properly or doesn't work as expected, you simply click the NoScript logo in the lower right of Firefox and allow the web site you're trying to view. Restricting scripting on web pages greatly enhances the security of your web browsing and reduces the probability of infection.