There are a number of attributes that make up the perceived performance of an instance. These can be greatly effected by badly coded scripts or a large number of them that are not required.
One of the most common ways scripting can cause perceived performance delays is when an excess of client scripts are used when a form opens. This causes a big delay in browser rendering and parsing, which is very apparent to the user. As we have mentioned before, a best practice in this scenario is to limit the amount of client scripts created only to those essential, and to ensure that server calls are kept to a minimum.
If information is needed for an onLoad client script, then consider a display business rule instead ...