On the http://ideaware.co/ site with the top nav the orange marker item underline moves (with a slight delay) smoothly as you hover over it.

I can see the list item blob in the source, but how are they doing this and how could i do something similar? Are there any jquery libraries for this type of thing?

<li class="blob" style="width: 35px; left: 0px; opacity: 1; overflow: hidden;"></li>

Thanks in advance