i am using jquery-ui dialog in my application. now i want to customize the signin/sinup dialog i.e. jquery-ui dialog. without customization dialogs are looking like:

but when i made following changes to login.jsp page that too in style it is changing all the dialogs of application that i don't want to happen but only signin/signup dialog. CSS code is:
.ui-widget-header {
    background: #343434 !important;
    border: none
}
.ui-dialog-titlebar-close{
    background: #1C1C1C !important;
}
.ui-dialog {
    background: #343434 !important;
    border: thin 1px;
}
and js code for this signin dialog (id="signinDialog") is:
$(document).ready(function() {
$("#signinDialog").dialog({
    width : 600,
    resizable : false,
    modal : true,
    autoOpen : false,
    position : ['top', 157]
});
 function openLoginPopup() {
    $("#signinDialog").dialog("open");
}
after these changes i am getting signin/signup dialog the way i want but the problem is this is changing jquery-ui dialog css for all application and looking like this:

I have been stuck in this issue from morning and tried lot of ways to resolve, like this but all fell flat. Atlast i have to ask this.
I want all dialogs remain same except signin/signup dialog after customization.
 
     
     
    