Hi CHRISinUSA, thank you for your reply. I thought as much, but needed to verify to be quite sure that that poster was wrong. In that same BBC article you provided a link for, there is a call-out, which states:
Scottish Royal titles
* Prince William and Catherine are known as the Earl and Countess of Strathearn;
* Prince Charles uses the title the Duke of Rothesay while in Scotland. He also has the titles Earl of Carrick and Baron Renfrew, Lord of the Isles, and Prince and Great Steward of Scotland;
* Camilla is known as the Duchess of Rothesay;
* Prince Andrew has the title Earl of Inverness.
I can see where that poster would be completely mislead. The "Scottish Royal titles" heading and the accompanying bulleted text: "Prince William and Catherine are known as the Earl and Countess of Strathearn." No they are not. They are known as The Duke and Duchess of Cambridge with the Earldom of Strathearn being a subsidiary title and one in which they personally would never use.
Also, look at how they made reference to Prince Andrew's title: "Prince Andrew has the title Earl of Inverness." That's the language the BBC should have used for Prince William's Scottish title, but they didn't. Strange.
I'm actually quite surprised that the venerable BBC would allow a mistake like this to go through. Well, I view it as a mistake and very misleading. Where are the editors for online content these days? It is getting worse and worse in my opinion.