JavaScript -- Setting value in textfield{resolved}

[System_Error]

I'm trying to make a simple calculator and whenever I want to add text to the textfield(say a number) it will show up, then will dissapear.

function display(number) 
{ 
         var x = document.form1.displayText; 
              x.value = number; 
}

This is how I'm doing it, but why is the text dissapearing right after it appears?
Note: This method is called whenever one of the number buttons is clicked.