Add-ons enhances browsing experience; however, they also decrease its performance in crucial activities like navigating to webpages and creating new tabs. This blog post highhlights how add-on developers can improve add-on performance, and how IE enables users to identify performance impact of their add-ons and stay in control of their PCs.
End-users and Add-on Load Times. IE8 enable users to see for themselves how their add-ons affect their browser performance. IE measures the load time for each enabled add-on every time IE initializes it. In "Manage Add-ons" dialog, IE displays average load time for each add-on based on last 10 initializations. You can access Manage Add-ons dialog via Tools Menu. With this information handy, users can choose add-ons they want to keep enabled, and maintain control over their browsing performance:
For Add-on Developers and Add-on Load Times: Measuring Add-on Performance