//Function to handle default button clicks
// Where user hits enter key while in a text field

function defaultButton(e, buttonid){ 
      var bt = document.getElementById(buttonid); 
      if (typeof bt == 'object'){ 
            if(navigator.appName.indexOf("Netscape")>(-1)){ 
                  if (e.keyCode == 13){ 
                        bt.click(); 
                        return false; 
                  } 
            } 
            if (navigator.appName.indexOf("Microsoft Internet Explorer")>(-1)){ 
                  if (event.keyCode == 13){ 
                        bt.click(); 
                        return false; 
                  } 
            } 
      } 
} 



//code behind 
//TextBox1.Attributes.Add("onkeypress", "return defaultButton(event,'" + Button1.ClientID + "')")