Avatar Hover Height is a new feature that allows you to adjust the vertical position of your avatar within some preset limits. This is a purely graphical tweak that does not affect your position for physics purposes. For it to work properly, both you and observers watching you need to be running a supported viewer, and need to be in regions that support the feature. Currently two channels on aditi have support included: hover_height (consisting of the regions Hover1 and Hover2) and DRTSIM-274.
More detailed notes on how to use the feature can be found at the Hover Height Project Viewer wiki page. Please submit bug reports for any problems encountered.