Below mediaurl you can define the refresh rate of the texture (per minute or per second). Note that refreshing the texture many times a second is heavy for the viewer. If you want to load the page just once when the avatar enters the world, then set refresh rate to 0.
The texture will appear black while the web page is loading.
Note that not all web pages work very well, f.ex. sites using javascript heavily may have problems showing up properly.
Also note that the refresh rate is meant for updating active on-screen content (i.e. Flash) like YouTube videos, not for reloading/refreshing the web page. See a solution for the latter matter here: http://www.cybertechnews.org/?p=468