Browser sends saments to server about changes, which have occurred in a document. It's reasonable to make interaction symmetric: server sends saments to browser to make some changes. This monitoring-in-browser does not require to write on JS, unlike way, stated in HTML 5. Whole list of saments, which server can sends to browser, is given in separete document. Saments <<>> and <> are also possible.
Presence of the following html-element in document's header means, that this document can be updated by self-activated process on server and have identifier 785 in that process