This will make your image transparent when you hover over it with your cursor.

PREVIEW

ADVANCED HTML

To change the transparency CHANGE:
(opacity=50)

TO THE FOLLOWING:

(opacity=0) - won't show an image on hover
(opacity=30) - more transparency on hover
(opacity=90) - less transparency on hover
(opacity=100) - no transparency on hover

The above picture is set at 50, which is half

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