You can style elements which contain specified attributes.  So two paragraphs could look different because one has a title and the other does not.

Create a new page a call it cssstyleattribute.html.  Insert a paragraph of text into the body element.  It can say anything.  Copy that paragraph so you have two.

Inside the opening p tag for the first paragraph only insert a title attribute with a value in quotes.  Again the value can be any words.

Save the page and hover over the first paragraph and the title text should appear.  You have done all that before.  Now add this new rule set to the embedded style sheet near the top of the page:

p[title] {
    color:white;
    background-color:black;
}  

Save and view.  The first paragraph is styled because it has the attribute title in it. 

You could also style anything with a title rather than just paragraphs.  Add a h2 element with some text and view the page.  Change the CSS to this:

[title] {
    color:white;
    background-color:black;
}  

Try the page and there should be no change.  Add a title to the heading and try again.