Blog looks good on Firefox but is a total mess on Internet Explorer 8

Well, thanks to some brainstorming by some good friends out in the land of the Internet, I determined that this problem was caused by a security plug-in called WP-Secure from https://www.sitesecuritymonitor.com. I found it by deactivating all plug-ins and the reactivating them one at a time, revealing the security plug-in to be the culprit. I have checked my blog in IE8 since making the change and it now displays perfectly. Thanks for your help though, and for the link to the validation site. One of these days I’ll figure out how to fix them!

Glad you discovered your problem. Most of my plugins are causing problems, though they all work in all the browsers (?). I’m leaving them be for the time being, but need help with certain forbidden codes I’ve been using.
For all the embeded youtubes on my site, I want them centered (see https://www.theamazingagingmind.com/2010/harvie-krumpet-claymation-teaches-a-lesson-in-living/). They show as centered on three browsers I use, but the Validation site says I can’t do it the way I’m doing it. Currently, I’m just putting <center> </center> tags around the whole object code. Forbidden. How would I go about centering these objects correctly?
Thanks!

Never mind. Got the answer from another thread (stuck the object within div tags).