Be default, written smilies are automatically converted to their image counterpart in WordPress. So typing a “:” and a “)” next to each other in a post or page’s content area results in displaying an image of a yellow smiley face when viewing the post. Super annoying in most cases.

Add this to your theme’s functions.php to disable this functionality:

add_filter( 'option_use_smilies', '__return_false' );