selector "div:first-child + p:first-letter" fails only in Opera and only if it is in an external style sheet.

It works in Opera if it is in-line and works properly in Chrome, Firefox, Edge, IE (haven't checked Safari). The Stylesheet also "validates as CSS level 3 !" in W3 CSS test.

Working properly, or course, means it selects the first letter of a <p> only if it immediately follows the first <div>

more precisely the CSS is:

.flowing div:first-child + p:first-letter {
font-size: 3.2em;
float: left;
margin-top: .1em;
margin-right: 0;
line-height: .7;
margin-bottom: 0; }