To get a little more information, try changing this:
$query = "SELECT * FROM item WHERE ProductId='$Prodid'";
$result = mysql_query ($query);
$row= mysql_fetch_array($result);
to this:
$query = "SELECT * FROM item WHERE ProductId='$Prodid'";
$result = mysql_query ($query) or die('MySQL error: ' . mysql_error() . "<hr>Query: $query");
$row= mysql_fetch_array($result);
var_dump($row);
Let us know what the output is (specifically, if an error message is outputted OR the output of the var_dump call).
EDIT: Also, welcome to PHPBuilder, hellz! Just a friendly note: when posting PHP code, please use the board's [noparse]
[/noparse] bbcode tags as they make your code much easier to read and analyze. I already added these tags to your post above, but just keep this in mind for the future!
EDIT2: Woops! I missed something. Carefully examine your code above; you define $ProdId in one place yet you try to use $Prodid in another. Make the capitalization consistent and see if that works.