GMail provides users with a feature called known as Markers. This can be used for marking an email as important or not important. These Markers are also used by the Priority Inbox type to classify important emails.
But if you are not planning to use the Priority Inbox or the Markers then you have an option to turn off as well.
Click the Options icon and select Mail Settings from the list of available menus.
In the Mail Settings page navigate to Importance markers section under the Inbox tab.
In order to hide the markers, click the radio option with label as No markers then click the Save Changes button.