error: object expected

[alleyCat]

Hi there, could anybody there tell me what are the possible reasons for the error : Object expected, I have created objects to use. part of my code is like this:<form name="calculator" action="" method="post" ><table><tr><td><input type = "text" name = "screen" id = "screen" size = "18"/> </td></tr></table><table><tr><td><input type = "button" name = "one" id = "one" value = "1" class = "btn" onClick = "add2screen(this.value)"/></td></tr></table>it's a javascript calculator, whenever I click on a button, the error message pop up!