I have a Mathematica 10.0 Notebook that uses Associations (http://reference.wolfram.com/language/ref/Association.html). I uploaded it to Wolfram Programming Cloud but the cloud interface produced a syntax error when trying to define an Association. Are Associations supported in Wolfram Programming Cloud?
I've also had a number of things that worked fine both in Mathematica 9 and 10, but threw unexpected errors in the Cloud. I haven't seen any pattern to that, it's definitely not limited to new functions, but also affects things like Graphics3D objects. So I suspect we just need a bit more patience with the Cloud coming out of its beta stages.
Thanks for confirming that Associations are supported by Wolfram Programming Cloud. The following screenshot shows the code and error message from the web interface:
This code was runnable in the Mathematica 10 Desktop version. I found that if I removed the carriage return after the "col = <|" input and changed the first line to "col = <| "Posted Date" -> 1," then the input was processed as expected. Interestingly, if I then reintroduced the carriage return bringing the input back to the original, it still processed as expected on subsequent executions.
User interface in Desktop and Cloud versions is very different and Cloud is in beta. I suspect there are still some matching functionality being developed.
Wolfram Cloud does support Associations. I had no problems using this function. Without your code and error message it is impossible to say more.