I also see this. I have a SEO tool I use that does not see the meta tags from WordPress SEO and the only thing different form my sites that work and don’t work is Yoast and his use of single apostrophe ( ‘ ).
The standard allows either, but all the examples show doubles.
http://www.w3.org/TR/html4/intro/sgmltut.html
“By default, SGML requires that all attribute values be delimited using either double quotation marks (ASCII decimal 34) or single quotation marks (ASCII decimal 39). “
If there is not a good reason to use singles, I recommend changing to doubles as it is more common. Other software may not fully follow the standard and not recognize our meta tags.
Yeah, the standard doesn’t say anything about. But I have never seen any site using single apostrophes. Reason I said that coz I had been using single apostrophe in some of the meta descriptions for few pages without realising that how they showed up on the html side. And now all those pages have no meta description shown when I run the site: operator on Google. Either I change the meta description on all those pages or rather I hack the plugin myself for the time being.
