If you use Safari’s Email This Page option (found under the action toolbar button or File > Share), Mail will create a new message with the URL already in the body. However, a toolbar appears just above the body (below the Subject box) with the option to change the webpage content that Mail sends:
Reader – uses Safari’s Reader feature (View > Show Reader) to strip the article and in-line images out of the page and just sends that; useful for articles and blog posts
Web Page – sends the full content (non-Reader) of the webpage as you see it in Safari
PDF – uses OS X’s built-in service for PDF-ing just about anything, then embeds it in the message as an attachment
Link Only – the default behavior of the Email This Page command that Safari and Mail have had for years
So far, I cannot find a way to change this default behavior in Safari or Mail. Anyone know if it can be done?