issue about a attribute "readonly" of component

[Ryan Pan]

Hi all,
    Is there anyone who can tell me why the attribute "readonly" of
component did not work.
    For example,
<input type="text" id="country" jwcid="@TextField" value="ognl:
basicInfo.country" readonly onclick="javascript:openWindow('popup');" />
I can still input value into the field "country",So I wanna why?

Thanks a lot,
Ryan.