I have been using GoDaddy website Builder for 10 years- back when it was called GoDaddy Website Tonight
This is their old drag/drop website builder and this video shows how they handle custom meta tags-Ning has a similar method in that at the bottom of a page on Ning you can choose to use the Ning generated meta data or use the text box to enter yourown
I always used this box to add the data I wanted Facebook to use using the Open Graph (OG) that facebook uses
It was really pretty simple- create the content- right click on the image in the content that I wanted FB to display- then select "Copy Image Url" and add it to the facebook meta data
I think both GoDaddy and Ning settled on this method for custom meta data because they got tired of trying to make their software parse the correct image/content for every page of every users website
Much easier to let the page creator control how the dat is displayed
Here is the godaddy website builder custom Meta Tag video
https://youtu.be/wdVeOO7DLlA
<meta property="og:title" content="Title Of The Webpage Content Is On" />
<meta property="og:image" content="URL of your Image Here" />
<meta property="og:description" content=" short description of what you are seeing here"/>
You can also add meta properties for videos and other media using the OG tags explained here
https://developers.facebook.com/docs/reference/opengraph/object-type/website/
updated by @derrickhand300: 04/15/15 10:50:36AM