The site is a useful presentation of crystallographic issues regarding packing of simple objects, like equal atoms (as in metals) or simple ions. The title, Crystal lattices, is too ambitious, because lower symmetry crystal structures, as found in most organic and complex inorganic compounds, are not treated.
The learning level is rather difficult and probably unsuited for an undergraduate student. I think the best use would be to complement a frontal lesson, with text and figures.
The text is not so easy to read, even typographically: use of letter p rather then the greek letter for number pi is disturbing. Drawings included in the text are good in quality and well illustrate the sterical concepts, that are sometimes hard for newcomers.
MDL drawings are very well done and are nice to use with Chime plugin. However, for those who don't have the plugin, the start orientation of the structure (the only one they can see) is not happily chosen: a skew prospective would show the sterical features better.