There are some IE-only websites such as Windows Update that don’t display or load properly in alternate web browsers such as Opera. MeadCo’s Neptune executable is an Internet Explorer rendering engine plug-in for Opera and Mozilla Firefox web browsers. This plug-in allows users to open webpages inside Opera 9.x using Internet Explorer 7’s rendering engine.

To install and use this plug-in:

1) Download and install Meadco’s Neptune plug-in from here
2) Copy npmeadax.dll from “C:\Program Files\Internet Explorer\PLUGINS” to “C:\Program Files\Opera\program\plugins”
3) Click here to add a custom button to your Opera navigation bar called “View in IE”. (Courtesy: OperaWiki)

Now whenever you encounter a website that does not render properly in Opera, simply click the “View in IE” button.

If you want to always open specific websites in Opera using Internet Explorer engine,

1) Make sure you have User Javascript activated (Tools -> Prefences -> Advanced -> Content -> Javascript Options -> choose a UserJS folder)
2) Download this User JavaScript and place it under the UserJS folder
3) Edit the 1IERendering.js to add websites that you always want to open using IE7.

Firefox users can download and install a plug-in called IETab that offers similiar functionality.