The width problem is caused by the input button styling. You've got it set to 38px.
<input width="351" type="image" height="79" src="
skncomplex.com.au/wp-content/uploads/2012/01/order-now.png
" value="Order" name="Order" class="default-input sale-orderbutton np inf-button" id="Order" style="width: 38px;">
Take off the style="width: 38px;"