Hello Frank,

If I am not mistaken, this is a default behaviour from the browser itself.
Mozila would postback the page if there is an error in the script or process. However, when WebButton calls alert, mozila will assume it as an error result. If you don't use any alerts but set the text/value or call the function from WebButton click, it surely works well.

Regards,
Handy

I am so sad to hear that!
I think I will use "alert()" usually.
But when I use HtmlButton,it display normal   on fireFox.

  <input id="Button1" type="button" onclick="myalert()" value="htmlBtn" />
 function myalert()
    {
  alert(1);
    }

Hello Frank,

Please try to call alert with using timeout in firefox.

E.g

   function WebButton1_OnClientClick(controlId, parameter)
        {
            var WebButton1 = ISGetObject(controlId);
            window.setTimeout(function () { alert("1"); }, 100);
            return true;
        }

        <ISWebDesktop:WebButton ID="WebButton1" runat="server" Height="20px" OnClientClick="WebButton1_OnClientClick"
            Text="WebButton" >

As I said before, it is browser behaviour. When it returns error from mozila. the page would postback.
Somehow, in mozila, calliing alert directly would also returns an error. If you put timeout, you will that the page won't postback.

Regards,
Handy

Any way,thanks Handy!