I have created a child theme using ftp and the site is running well. But problem is when I am opening appearance > editor from dashboard the child theme style sheet is displaying blank page where from ftp server the style sheet looks everything okay with all it's codes and characters.
Make sure the styles.css in the child theme folder has the proper tags (opening and closing).
Child themes, when first created, usually have a blank styles.css file, with just the open/close 'styles' tag.
Although probably not the answer, perhaps extra spacing is before the opening tag? (Shouldn't make a difference if there is...)