According to Jakob Nielsen, people are most productive if the computer's response to their click takes less than a second.
People lose their concentration if a page takes longer than ten seconds to appear.
Of course, computers get more powerful and bandwidth increases continually, at least on average. But at the same time new devices are being connected to the Web, such as mobile phones and TVs, and they are much slower. They too will improve, eventually, although they will probably always be behind desktop computers. Designers of Web technology will always have to consider efficiency. When designing formal languages to write resources in, designers should ensure that the languages are easy to parse and reasonably compact.