This tab displays the parameter names and values contained a POST request. The mime type displayed on this tab is the encoding scheme used to upload data and if usually one of the following for HTML based forms:
This is the same format as a query string, but the string is passed in the request body rather than the URL.
This passes the raw, unescaped data in the the POST body by using a marker to define the data boundaries.
If required, you can view the network low level format of an HTTP POST request in the Stream tab in Internet Explorer.
The size column shows the total size in bytes of the parameter name and value in the HTTP request message.