Agree with Eugene. I prefer the most basic of formats that can be loaded up ANY system or software. I remember having data on an old MAC. The word processing and spreadsheets files transfered to Windows platforms easily but the other data written by specialized software had to be left out.No way of transfering them.

That was an eye opener.

However, having said that, it seems that most people have MS Word & Excel. And so it would seem safe enough to assume they would be there in some time.

I save webpages like this one as an MHTML ( the web-ARCHIVE format ) , that allows saving everything in it in one file, instaed of using htm, or html format that saves the webpages in one file plus one folder for images. I hope those single-file archives would be reable for some time.