a = 10 // a=numbers of banners
var slump = Math.random();
var talet = Math.round(slump * (a-1))+1;

function create() {
        this.width = ''
        this.height = ''
        this.src = ''
        this.href = ''
                 this.border = ''
                 this.target = ''
}

b = new Array()
for(var i=1; i<=a; i++) { b[i] = new create() }

b[1].src    = "immagini/_1.jpg"
b[1].width  = "560"
b[1].height = "330"
b[1].border = "0"

b[2].src    = "immagini/_2.jpg"
b[2].width  = "560"
b[2].height = "330"
b[2].border = "0"

b[3].src    = "immagini/_3.jpg"
b[3].width  = "560"
b[3].height = "330"
b[3].border = "0"

b[4].src    = "immagini/_4.jpg"
b[4].width  = "560"
b[4].height = "330"
b[4].border = "0"

b[5].src    = "immagini/_5.jpg"
b[5].width  = "560"
b[5].height = "330"
b[5].border = "0"

b[6].src    = "immagini/_6.jpg"
b[6].width  = "560"
b[6].height = "330"
b[6].border = "0"

b[7].src    = "immagini/_7.jpg"
b[7].width  = "560"
b[7].height = "330"
b[7].border = "0"

b[8].src    = "immagini/_8.jpg"
b[8].width  = "560"
b[8].height = "330"
b[8].border = "0"

b[9].src    = "immagini/_9.jpg"
b[9].width  = "560"
b[9].height = "330"
b[9].border = "0"

b[10].src    = "immagini/_1.jpg"
b[10].width  = "560"
b[10].height = "330"
b[10].border = "0"

var visa = "";

visa += '<img src="'+b[talet].src+'" height='+b[talet].height
visa += ' width='+b[talet].width+' border='+b[talet].border+'>';