If there is one thing that I've learned in my 1, 2, 3,....., 12 years on the internet is that stuff doesn't stay on here for very long. Images, PDFs, heck even HTML content won't be staying where it is for long. Sure it may be there for the next 5 years or so, but after that? Perhaps it won't be there.

There are many sites I liked, some associated with televisions hows that have since been cancelled or saw a complete run and are now in syndication, that simply don't exist anymore. Sure you can head over to archive.org and see what websites looked like back in the day, but archive.org doesn't do a complete saving of those websites. Images you wanted may no longer the there. Some content you wanted may not even be there.

So the lesson is: if you like something on the web, and it's freely accessible today - grab it! Save it! Put it in a safe place if you want to make reference to it later. Save a URL where you got it from as well just in case you need to cite it in a paper or something :-)