Welcome to the Q&A Forum

Google will see the content as plain text, check for example seobrowser.com. However, there is a chance that Google is parsing the CSS to find out that this particular content is hidden, and therefore devalues it. I don't recall ever reading about this, but it would make some sense because many visitors won't see the text.

Ok - I will ask something else which might help (and which I might understand). From reading around, I understand that search engines will index pages with ?category=foo&subcategory=fee on the end. Can anyone confirm this, as if this is true it will make my life a lot easier! Thanks