Case Sensitivity

Aside from list TYPE attributes (OL TYPE="a") what are some examples of when HTML programmer's should be aware of case sensitivity?

I know that the use of Java applets is one area are there some other examples?

Are there some readability standards for putting some code elements in upppercase and others in lowercase?
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brunoConnect With a Mentor Commented:
Ernest I hate to prove you wrong but...

In CURRENT HTML 4.01 standards it states
"Element names are written in uppercase letters (e.g., BODY). Attribute names are written in lowercase letters (e.g., lang, onsubmit). Recall that in HTML, element and attribute names are case-insensitive; the convention is meant to encourage readability."

accessible at :

If you would like more info on the conversion of HTML to XHTML please check:

The reason to use lowercase is because of HTML's conversion to XHTML, which is XML based and has VERY strict standards.


How about closing off this question?  I think you should be able to accept webwoman's answer and PAQ this.  Webwoman if panrob does not return, I suggest proposing an answer as you were correct.

xhtml/xml requires tags in lowercase. Some servers (actually a lot of them) are case sensitive for file names. Javascript is case sensitive -- for some things, not for others.

To maintain compatibility going forward, it's safest to use lowercase for HTML tags, the required case for javascript, and lowercase for filenames. It also makes it a lot easier when you're debugging. Since it doesn't apply to everything, having an error come up because of a misplaced upper/lower case word/filename can be a real pain in the butt to figure out.
I suggest picking one and sticking with it. I am lazy I use all lowercase.

Unix servers are case sensitive, so if you have a reference to an image in your html img src=Picture.jpg and the picture is actually named picture.jpg you will have a problem.

HTML comments or Include files I will use CAPS just to make the code stand out a little bit.

Jim S.
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follow webwoman's advice.

HTML is going away, to be replaced with XHTML v1.0.  XHTML requires ALL tags be lowercase.  it also requires all tags be closed (even <br / > )

Whether HTML is going away, as brunobear thinks, should not be a matter of concern.  The current standard says all tags should be lowercase.  The older standards (and some books!) say upper or lower is OK.  Echoing others and adding my voice: You're better off using all lowercase tags for HTML.
brunobear: Thank you very much for proving me wrong!  When I am wrong and someone provides a respected reference proving it then I appreciate the correction.  Thanks!
Ernest, no problem.

I knew you were wrong but wasn't sure I was going to be able to find the correct reference to prove it.  Thankfully I did.  :-)

now we just gotta get panrob back here to clean up this question....

panrobAuthor Commented:
sorry I was away on vacation and did not take my laptop
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