Whether on purpose or just putting in a link to another site.
Not for CSS or JS files, just general links in the body section. Should I be adding the WWW in there? I know that it will still go to the page without fault. But someone had told that it will effect SEO and the way Google looks at links? Is this true?
Is Google still in the stone age that a simple www would be effected?
I've gotten into the habit because I'm a windows user (have tried linux before, but prefer Windows) and I type in links like 'site.com' into my browser bar, and don't even have to worry about putting in HTTP let alone WWW.
-- In conclusion --
Will a missing 'www' in a link on your website effect your SEO and the way Google looks at the link?
The use of www or non-www is largely a matter of choice. Consistency is the key, so whichever you use, just stick with it for that site, all links in the site, external links, etc should all point to your choice.
In their webmaster tools, Google refers to this as the 'preferred domain' and recommends simply setting a 301 redirect to ensure you always use your preferred format.