Is it just a certain WWW site or all WWW sites?
If it was a problem with your system you would see the problem on all sites (that use scripts).
I'm pretty sure that there is not going to be much you can do about that message because the problem is not with your system.
The script that is running slow is a script on the WWW page you are visiting and Internet Explorer is letting you know that it is waiting for the script on the WWW page to finish... and it is taking a long time. It could be the WWW site it slow, the script
they wrote has some errors or it poorly written. It is their problem, not your problem.
How about this site (the MS Answers site) - does it generate the same error message?
If it is not an invasion of your privacy you should provide the link/URL to the WWW page you are visiting when you see the message.
Since we can't see what you are seeing you should provide a screenshot of the message and this link tells you how to include a screenshot in your post
How to include a screenshot if your post
IE has some options that allow you to disable those messages and it will not make things run faster or fix errors in the scripts on the WWW page you are visiting but you won't see the messages anymore.
In your Internet Options these adjustments are very common to prevent those annoying popups about problems on WWW sites that have those issues:

It won't "fix" the problem because the problem is not with your system - it is with the WWW site you are visiting.
But you won't see the messages anymore.
Internet Explorer is one of the worst browsers on the planet so you can consider other popular free alternatives like:
Firefox
Google Chrome
You can still use IE if you want to or have to and you can have all three installed on your system at the same time.
None of that will fix the script problem on the WWW pages you are visiting though.