TargetAlert is an extension for the Firefox web browser that provides visual cues for the destinations of hyperlinks. If a hyperlink points to a something that is not a web page, then TargetAlert will try to append an icon to the hyperlink that represents its destination. This has two main advantages over plain hyperlinks. First, it makes links to PDF documents easier to find on a web page. Second, if you do not enjoy the "surprise" of clicking on a hyperlink and discovering that it links to a PDF document, you can use TargetAlert as a visual warning.
I just installed it