// =======================================================================
// This function randomly replaces image in the image element "gisDayImage"
// with one of the four possible images and alternate texts
// =======================================================================
function loadGISDayImage ()
{
    var altArray =
    [
        "I support GIS Day",
        "Join the celebration, visit GIS Day",
        "GIS Day",
        "Proud Participant in GIS Day"
    ] ;

    var imgElement = document.getElementById("gisDayImage") ;

    if (imgElement != null)
    {
        var imgIndex = Math.floor (Math.random () * altArray.length) ;
        imgElement.src = imgElement.src.replace(/web-link[0-9]*/, "web-link" + (imgIndex + 1)) ;
        imgElement.alt = altArray[imgIndex] ;
    }
}