I found a high pr -domain from Drophunt.
I checked the validity of the pr, it showed green. I bought it.. and ding! The pr shows red.
So..
1. Is this normal?
2. Is there something to do to make it valid again? Or can I so something when registering a domain like this?
3. Can I still sell it as prX-domain?
it probably wasn't valid pagerank to begin with - especially if it was a high pr domain. it would be wrong to sell it as a prx domain because it isn't.
next time check pagerank with one of those "fake pagerank checkers" before buying.
Next time, you should check with google toolbar. Download one and install it in your computer.
For your case, it may come from following reason.
-before you bought: domain was forwarding to a high pagerank domain. When you check it gives you pgrank from that domain.
- after you bought: domain no more forwarding to the high pgrank domain ==> pgrank dropped
1. there are people who cheat you know i guess it's normal.
2. develop, fill with content and promote
3. nope
to test any pr domains to see if it's valid type
cache:thedomain.com replacing thedomain.com with actual domain name and see if it's pointing to it's contents so it's valid if it's pointing to another site pref. google or other higher pr sites not it's own then it's fake.
I scooped up a "valid" PR5 domain once after a drop, showed "valid" with the site I used, turned out to be a redirect to a popular blog. Cheap, but very valuable lesson for 8 dollars. In my opinion if you buy a dropped or whatever,,, PR domain you should do a check on http://www.seologs.com/pr-check/pagerank.html for a good PR check first, and then http://www.archive.org and see if you can continue what the draw was at the domain/site you are interested in rich from
Good Luck
btw, I am not affiliated with either site, I have just found them very useful.
Dropped pr-domains? 
