I\'ve got a fairly ajax heavy site and some 3k html formatted pages are inserted into the DOM from ajax requests.
What I have been doing is taking the html responses
In some cases, AJAX responses need to return more information than just the HTML to be displayed. For example, let's say you are returning a list of the first twenty items from a search. You may need to return the total number of search results to be displayed somewhere else in the DOM. You could try piggybacking the total count in a hidden div, but that can get messy. With JSON, the total count can simply be a field value a structured JSON response.
Here are a few pros for sending JSON/XML instead of HTML:
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tags which allows cross domain AJAX scenarios