viewportwidth = null;
viewportheight = null;
function decideSizes(){}
function getDimensions() {
if (typeof window.innerWidth != 'undefined')
 {
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      viewportheight = window.innerHeight
 }
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 {
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 else
 {
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       viewportheight = document.getElementsByTagName('body')[0].clientHeight
 }
decideSizes();
}
window.onload = getDimensions();

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