No, silly, not the MHSA website, the Mennonite Genealogical Data Index website, or this MHSA Blog, but lots of other sites get updated/changed and you no longer can find the information you dearly wanted to follow up on.
The answer to your problem is a wonder resource called the "Wayback Machine".
This is an online, non-profit initiative to 'archive' old webpages (generally devoid of graphical content). So, if you want to look at a previous version of a website (or specific webpage), or a website that's gone offline, this is a likely answer to your problem.
Just go to www.archive.org and type in the former address and it will lead you to Wayback Machine's version of a "hit list.
For instance, one of the very first webpage that I built for a family history organization was one for the Alberta Family Histories Society here in Calgary: www.afhs.ab.ca.
The Wayback machine has a 1999 copy (http://web.archive.org/web/19990125093039/http://www.afhs.ab.ca/), a 2001 copy (http://web.archive.org/web/20010117181800/http://afhs.ab.ca/), a 2003 (http://web.archive.org/web/20030126102912/http://www.afhs.ab.ca/), etc.
In the last few years others have developed the pages, and so it looked like this at the beginning 2007 http://web.archive.org/web/20070128064731/http://www.afhs.ab.ca/index.html
Now - you don't necessarily care about those homepages or the AFHS, but what if family history information were only available online, and the owner of the pages disappeared, and you wanted to salvage the information that's gone?
I had exactly that experience with Hugh Armstrong's wonderful pages in BC. and was able to retrieve his data and republish it on the AFHS website (see: http://www.afhs.ab.ca/publications/armstrong/).
The work you do may be impacted by the "version" of a webpage published at different points in time (The Wayback Machine is a way to see what the earlier message was.
Judii - for the Mennonite Historical Society of Alberta.