Recently I've been seeing a lot of this:
<a href='http://widget-site-example.com/example.html'>
<img src='http://widget-site-example.com/ross.jpg' alt='Ross's Widget' />
</a>
Is it valid to use single quotes in HTML? As I've highlighted above it's also problematic because you have to escape apostrophes.
It's certainly valid to use single quotes (HTML 4.01, section 3.2.2). I haven't noticed such a trend, but perhaps there's some framework that powers web sites you've visited that happens to quote using single quotes.