Query-string caching

Each unique query string can be a different cache key.

• Ignore query strings — one object, but ?ver=4.2 after a plugin update may not show.
• Include query strings — updates show, but ?foo=1 and ?foo=2 fragment the cache.

Prefer filename hashing (app.91c3.css). If you cannot, enable query-string caching only on wp-content / wp-includes. WordPress guide covers the W3TC interaction.