When the browser encounters a <script> element, it pauses web page rendering activities while it retrieves and then executes the script. You can use the defer attribute to prevent the script from being processed until it is called. Unless the initial web page content relies on the outcome of a script, you should use the defer attribute.
Script processing behavior varies slightly, depending on the network gateway the browser uses to access the content.
The BlackBerry Browser supports a number of compression algorithms. In general, compressing content targeting the BlackBerry Browser offers little benefit in terms of reducing data transfer speeds or network traffic; if the content is accessed through the BlackBerry MDS Connection Service network gateway or the BlackBerry Internet Service Browsing network gateway, the network gateway unpacks the script before it compiles and recompresses the script for efficient transfer over the wireless network. If you use compression algorithms that contain the eval() function, the algorithms can hinder performance; the network gateway will unpack and recompress the script for transfer, but since the network gateway cannot precompile the enclosed code, the benefit derived from precompiling on the server side is reduced.