A basic technique for dynamic web application is to use a hidden iframe HTML element (an "inline frame", which allows a website to embed one HTML document inside another). This invisible iframe is sent as a chunked block, which implicitly declares it as infinitely long (sometimes called "forever frame"). As events occur, the iframe is gradually filled with codice_1 tags, containing JavaScript to be executed in the browser. Because browsers render HTML pages incrementally, each codice_1 tag is executed as it is received. Some browsers require a specific minimum document size before parsing and execution is started, which can be obtained by initially sending 1–2 kB of padding spaces.