how to open drupal login and signup form on modal form. I just want to open login form in modal box as per semantic ui framework http://semantic-ui.com/modules/modal.html. I just want to use this framework. Is this possible with theming or custom module is require for this.

Any help would be appreciated.
You should include the necessary javascript in your theme .info file or template or module with drupal_add_js() , then you should use the code defined in the link you provide to target the element that you want to apply the functionality too. This elememnt may be generated by a module that specifies a theme function and uses a template (tpl.php) file in which you would put your markup.