Relative positioning in Safari

.progressImage
{
  position:relative;
  top:50%;
}

.progressPanel
{
height:100%;
width:100%;
text-align:center;
display:none;
}

<asp:Panel ID="pnlProgress" runat="server" CssClass="progressPanel">
<asp:Image ID="Image1" runat="server" CssClass="progressImage" ImageUrl="~/Images/Icons/loading.gif" />
</asp:Panel>

.progressPanel
{
  height:100%;
  width:100%;
  position:relative;
}

.progressImage
{
  position:absolute;
  top:50%;
  left:50%;
}

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
    <head>
        <title>Test</title>
        <style type="text/css">
        body {
          height:700px;
        }
        .progressImage {
    	  position:absolute;
    	  top:50%;
    	  left:50%;
    	  margin-left:-16px;
    	  margin-top:-16px;
    	}

    	.progressPanel {
    	  position:relative;
    	  height:100%;
    	  width:100%;
    	  text-align:center;
    	  background:red;
    	}
        </style>
    </head>
    <body>
    <div class="progressPanel"><img class="progressImage" src="pic.jpg"/></div>
    </body>
</html>

.progressPanel
{
    height:100%;
    width:100%;
    text-align:center;
    display:none;
    position: relative;
}

background: url('path/to/image.gif') no-repeat center middle;