Links with an
up-preload attribute will silently fetch their target
when the user hovers over the click area, or when the user puts her
mouse/finger down (before releasing). This way the
response will already be cached when the user performs the click,
making the interaction feel instant.
The number of milliseconds to wait between hovering and preloading. Increasing this will lower the load in your server, but will also make the interaction feel less instant.