That Id is for an object called
Here's how you can find that out for yourself in the future (if you're open to Execute Anonymous).
Id someId = Id.valueOf('00Ng0000000p6b6');
I do not see this
sObjectType in my Salesforce Schema (Eclipse), but I haven't looked through a WSDL for it. If you need to programmatically reference it for your selectors, it may make sense to manually find the Ids and store the values in a custom setting. I think if you use a hierarchy custom setting it will be easier to reference on the page. Just add a field for each related list you want to search, and store the Id in it under the org default.