There are some exceptions, but they will be obvious. If something doesn't work, first check carefully, then try variations. Just knowing where these are will be helpful in the not too distant future. In fact, you'll be playing with computer molecular modeling next week. It is a short movie loop, well worth viewing.
Some sites are simply collections of other sites, but they are quite useful.
A single bookmark can lead to many hallways and many doors. You'll probably want to revisit these link sites a few times in order to get a real feel of what all they have to offer. Try this link site. Go to file, and open a new browser window. Now you can explore some links in one, while you have one as an easy home-base.