Gmail predicts which emails might be of high importance to you so it marks them as important with a yellow icon. If your inbox ends up full of so called important emails, this is how you disable this feature.
If there is a vast number of unimportant unread emails accumulating your Gmail inbox and it's starting to bother you, but you don't have time or nerves to mark them as read page by page, this is what you can do.
A really great Gmail functionallity that enables you to send emails from your other email addresses using your main Gmail account. Let's find out how to add other addresses to your account.