img{max-width: 600px;max-height: 800px;}

var img_width = img.OffsetWidth;<BR>var img_height = OffsetHeight;
var current_w = (150*img_width)/img_height;
var current_h = (330*img_height)/img_width;
if(img_height>150){
if(img_width>330){
D.css(img,{
width:330 + "px",
height:current_h + "px"
})
}else{
D.css(img,{
width:current_w + "px",
height:150 + "px"
})
}
}else{
if(img_width>330){
D.css(img,{
width:330 + "px",
height:current_h + "px"
})
}else{
D.css(img,{
width:img_width + "px",
height:img_height + "px"
})
}
}