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/']
It depends on the implementation of your JSON writer/parser. Microsoft's DataContractJsonSerializer seems to have a hard limit around 8kb (8192 I think), and it will error out for larger strings.

Edit:
We were able to resolve the 8K limit for JSON strings by setting the MaxJsonLength property in the web config as described in this answer: <https://stackoverflow.com/a/1151993/61569>
What is the requirement? Are you trying to send a large SQL Table as JSON object? I think **it is not practical**.

You will consume a **large chunk of server resource** if you push thru with this.
You will also not be able to measure the progress with a progress bar because your App will just wait for the server to reply back which would take ages.

What I recommend to do is to chop the request into batches say first 1000 then request again the next 1000 till you get what you need.
This way you could also put a nice progress bar to know the progress as extracting that amount of data could really take too long.