Please post in the correct forum.
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Use this code...
#AD1066A_Animation_SubscriberExperienceGUI_Insight_1920x1080 {
max-width: 100%;
}
To create a custom CSS compatible with Gantry 5 please read this
http://docs.gantry.org/gantry5/tutorials/adding-a-custom-style-sheet
.
Remember to recompile CSS from base outline too.
Regards, Mark.