Hi Pil Lee,
It is safe to ignore, delete, or comment out that line 73 of code from the view.php file for Skype. All it does is add a button in a place and style that has been deprecated, and no longer used.
Personally, I just have deleted it.
Also, if you follow Howard's suggestion and read through the comments he linked to, there are a few other changes you might like to make based off the info listed there.