Copyright, Registered, and Trademark Symbols
To display any of these symbols in your HTML document, use the following codes:
Copyright Symbol © - © or © or ©
Registered Symbol ® - ® or ® or ®
Trademark Symbol ™ - ™ or ™ or ™ or ™ or ™
Sound Recording Copyright ℗ - ℗ or ℗
Service Mark ℠ - ℠ or ℠
DOCTYPE or DTD
Amazing how you can be doing web work for such a long time and miss something completely critical. I believe heartily in creating standards compliant web pages and have always been frustrated by IE not rendering the same as Opera or Firefox. Today I may have figured out why. It's the DOCTYPE declaration at the top of my HTML code.
When IE5 for the Mac was designed, it came with a new idea: doctype switching. Because older versions of IE handled certain rather important details in the CSS specification incorrectly, there were some issues with suddenly starting to do it right. The web had a few million pages that required the incorrect handling in order to display as the author had intended. Doctype switching means that the browser checks the doctype declaration of the document, and then makes an educated guess about whether the author is likely to have followed the W3C's standards or Microsoft's.
Most modern browsers now apply doctype switching, so the doctype declaration does actually have some significance even for browsers. That was not the original intention, though.
For more information look here: