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For spped up of wordpress, I have installed [Jetpack by WordPress.com].
But, Lightbox does not work with Photon(Free CDN services) of Jetpack .
This is a note of solution at that time.
Lightbox doen't work with Photon(Jetpack)
Lightbox plugin is "Simple Lightbox"
rel = "lightbox" is not added
Lightbox(Simple Lightbox) does't work When I activate the [Photon(Jetpack)],and images are displayed other window.
Link of the image is rewritten by activating the [Photon], I cleared cache and stopped Minify plugins (WP Minify), but the problem did not resolve.
Install [WP Lightbox 2] plugin
I found a solution with the same situation in the forum of WordPress.
Lightbox doesn't work with Photon(Jetpack)
The problem has been going on in the combination of [Photon(Jetpack)] and [Simple Lightbox].
The cause of the problem does not seem to know well in the forum. However, it is solved by using [WP Lightbox 2] plugin.
[WP Lightbox 2]
As a result of experiment with this web site(ww.amelt.net) , it worked without a problem.
By the way, before you install the [WP Lightbox 2] plug-in, it is better to perform the following procedure.
1.Stop the Lightbox plugin
2.Clear all caches
3.After that, install/activate the [WP Lightbox 2]