[jQuery] How to prevent third-party CSS code override our CSS

[jQuery] How to prevent third-party CSS code override our CSS

I'm using sortable of jQuery UI!
My elements  such as UL tag, LI tag(sortable, dragable,..element) may put into many template!
And each template have thier own CSS, so, that CSS override CSS of my LI tag
Have anyway to clear all CSS apply on our element, then apply new CSS? Or i must use !important for all property to prevent overriding!
Take a look on two URL:
<a href="http://trademerchants.com/delnow/kurei/dnd//themes/hr/html/index.myTemplate.php">http://trademerchants.com/delnow/kurei/dnd//themes/hr/html/index.myTemplate.php</a>
<a href="http://trademerchants.com/delnow/kurei/dnd//themes/template1/html/index.myTemplate.php">http://trademerchants.com/delnow/kurei/dnd//themes/template1/html/index.myTemplate.php</a>
As you can see, <li> item appeas in other style because each template have own CSS
Does anyone know how to prevent this?