It is a common practice of ISP's to cache any possible file from downloading it again. As an overall result this will save ISP's lots of bandwidth although you paid for your internet download not for ISP to client download.
In many situation this may cause a problem whether you are web developer or system admin. When downloading a files from a new website you are developing you always get old versions of files. This also applies if you are using unix tool wget. To get around this problem one needs to include an option --no-cache to wget command . This way wget will send an appropriate directive, in this case Pragma: no-cache to a remote server to retrieve a new version of requested files.
wget --no-cache http://www.<remote server>/remote-files*
If you are not using wget and you are web developer you may consider to temporarily add a meta tag to your pages with Pragma: no-cache directive to avoid ISP caching problem.
<meta http-equiv="pragma" content="nocache">