I want to be free

Funny, but indexOf method doesn’t work in an empty array in Internet Explorer, the method is just not defined. Eh!

Forget about that and always use jQuery wrapper –

$.inArray(42, [31, 42, 53]);

I added a jQuery plugin called add2cart.

This plugin implements visual effect of adding something to cart (busket). Visually it’s similar to Microsoft Word post-save visual effect, when a gray rectangular of page moves down to the toolbar.

Example of usage:

<input type="button" value="Add to cart"
  onclick="$.add2cart( 'product1_id', 'cart_img_id'  )" />

You can try it out at demo page.