Sends a header to the browser. The HEADER keyword requires two parameters: the name of the header, and the value of the header.
Because headers and cookies must be sent before any data, the HEADER keyword must precede any data in the template, including spaces, tabs, carriage returns, and line feeds. The easiest way to ensure that no data is sent before the HEADER keyword is processed is to include the NOOUTPUT keyword as the very first item in the template, followed by the HEADER keyword and the OUTPUT keyword, as shown in the following example:
{NOOUTPUT}
{HEADER "pragma" "no-cache"}
{OUTPUT}
. . .
For more information about the NOOUTPUT and OUTPUT keywords, see NOOUTPUT and OUTPUT.