1. Sometimes I download a video and when it is done dowloading I try to open it, it doesn't open, then I hold my mose over it to realize that it is zero bites or bytes I don't remember, how do I know that something that I download will basically be nothing?

2. When I search for a video there are usually some mpeg, mpg, avi, then there is a bunch of quicktime files. I try to download those but all they ever do is open a internet site, or if I do download it is something I didnt want to download. (I also notice that alot of quicktime files are 1,050 megabytes or kilobytes, something like that Im not sure). So the question is, are any quicktime files ever good, as in not a internet site or something I didn't want?

3. Last one, I download a video file and I try to open it and it says it is unsicure, why?

Thanks if you answer