Whilst the website does contain help pages containing information, it is no substitute for a textbook. Refer to a copy of a periodic table whilst carrying out the exercises.
This site was developed using Chrome and it also works as expected in Edge, Firefox, Safari, and Opera. Scripts need to enabled in the settings. It may sometimes be helpful to disable the keyboard shortcuts (alt+p, alt+n, and alt+b) which are used by some browsers. The scripts do not work for me when I use Internet Explorer (V11): It may be that Internet Explorer can be made to work with the appropriate settings. The software works both with keyboard and touch screen input.
These pages are straightforward: you just fill in the missing information on the interactive table.
Students often find the numbers in chemical formulae, written as subscripts or superscripts, confusing. In the formula and equation pages, you must get the formatting correct. Whilst it is not possible to show formatted text within a text input box, your formatted answer appears below the text box as you type. You can set the font (Normal, Superscript, or Subscript) by clicking the appropriate option button as you type. An alternative is to use a keyboard shortcut (alt + ‘n’ for Normal, alt + ‘p’ for superscript and alt + ‘b’ for subscript: on a Mac you press ctrl + alt + 'n', 'p', or 'b').
That is all you need to know so, go ahead, use the site and learn some chemistry!