The website is from 2001 and looks like yet; however, it still has alot of information that is somewhat easy to access and (more easily to) understand. The main page of Wild World is a zoomable map of the Earth. One can browse the area of interest and find the code of various ecoregions. Then, the next step is to go to the Ecoregion Index and look up the code. Then, when found one can read the National Geographic brief article or scroll down and read click to read the full World Wildlife Foundation report. An example of both reports can be viewed here with NatGeo's and WWF's Central Tall Grasslands articles.
The age does show but if one needs to look up ecoregion information this is a good source to try which most teachers would accept a citation from.