What is the difference between XHTML and HTML?

all labels must be lowercase
In XHTML, all labels must be lowercase, not case-insensitive, and not all uppercase. Examples are as follows.
Fatal error:Correct:The labels must be paired.
such as <p>...</p>, <a>...</a>, <div>...</div> tags, etc., when a label appears, must have a corresponding end tag, indispensable, Just like the parentheses in any programming language.
Error: Everyone good <p> is really good

correct:<p> Everyone good </p><p> is really good </p>

Summary:

label order must be correctly labeled from outside to inside, layer by layer covered, so suppose you write div first write H1, end will write H1 after writing Div. Just remember a principle of "advanced out", first pop the label to the end.
error:<div>
correct:<div>
all attributes must use double quotation marks
in XHTML 1.0, a single quotation mark cannot be used, so you have to use double quotes throughout the process.

error: <div style=font-size:11px>csdn</div>
correct: <div style= "font-size:11px" >csdn</div
5
target= "_blank" is not allowed
The target property is completely banned from XHTML1.1, and if you want to have the ability to open a new window, you must rewrite it to rel= "external" and work with JavaScript to achieve this effect.

error: <a href= "http://blog.mukispace.com" target= "_blank" >csdn</a>
correct: <a href= "http://blog.mukispace.com" rel= "external" >csdn</a>