I am using jquery, JSON, and AJAX for a comment system. I am curious, is there a size limit on what you can send through/store with JSON? Like if a user types a large amount and I send it through JSON is there some sort of maximum limit? 

Also can any kind of text be sent through JSON. for example sometime I allow users to use html, will this be ok?
['https://Stackoverflow.com/questions/1262376', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/143030/']
There is no fixed limit on how large a JSON data block is or any of the fields. 

There are limits to how much JSON the JavaScript implementation of various browsers can handle (e.g. around 40MB in my experience). See [this question for example](https://stackoverflow.com/questions/4833480/have-i-reached-the-limits-of-the-size-of-objects-javascript-in-my-browser-can-ha).
Surely everyone's missed a trick here. The current file size limit of a json file is 18,446,744,073,709,551,616 characters or if you prefer bytes, or even 2^64 bytes if you're looking at 64 bit infrastructures at least.

For all intents, and purposes we can assume it's unlimited as you'll probably have a hard time hitting this issue...