How to preload background image in tag ?

 
Hi There!
I am looking for JavaScript/CSS/C# code for preload the background image (imgBkgd2360.jpg) for the <body> tag in the WEBSITE.master file for my ASP.NET 4.0 website.
The full <body> tag is shown below:
<body style="margin:0 auto;width:100%; background-image:url('Images/imgBkgd2360.jpg');  padding-top:20px; font-family:Arial; font-size:10pt;">
Thanks,
May

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