Data sent from a Web browser or other HTTP client to a Web server. Data such as search words for a query and fields in a fill-in-form are commonly transferred with the POST command. When users click back to a Web page that previously issued a POST, they are generally confronted with a warning that tells them the data on the previous page will be resent to the Web server. For example, if the previous page submitted an order, the submission will be repeated.
These messages from Firefox 2 and 3 (top and middle) warn the user that a financial transaction may be repeated by returning to the previous page. While Firefox 2 mentions POSTDATA, Firefox 3 omits technical terms including cache. The bottom message from Google's Chrome browser uses no jargon and even omits the example of an online order.