What is dividend?
Each year public companies announce how much profit they will share with a class of stock holders. This is called a dividend. They can be in several forms: cash, more shares or other assets.
When trading shares, dividends will be credited/debited from your account after the market closes. Shares CFDs usually gain or lose value before this expected announcement and it reflects on the market. So, this increase or decrease in price usually offsets the dividend credit/debit.