It seems that you have a setting enabled “Enabled Template Path Hints for Storefront”.
Follow the steps to disable it:
1.login as admin
4.Here you will find a setting as Debug
5.click on "Debug" you see that following tab are present:
-Enabled Template Path Hints for Storefront
-Enabled Template Path Hints for Admin
-Add Block Names to Hints
6.Currently “Enabled Template Path Hints for Storefront” would be enabled which is why you are getting those red lines. So all you have to do this is to simply disable this setting.Just do this Enabled Template Path Hints for Storefront=no.
7.save the setting and refresh the Main Website where you were getting this error. You will notice that those red lines are gone.
Hope this answer was helpful.