We use XHTML standards for all web page.
It is some thing need to be care for.
Open with the proper DOCTYPE and namespace.
Declare your content type using the META Content element.
Write all element and attribute names in lowercase.
Quote all attribute values.
Assign values to all attributes.
Close all tags.
Close “empty” tags with a space and a slash.
Do not put double dashes inside a comment.
Ensure that less-than and ampersand are <lt; and &
Sometimes the errors are come from the mistakes above. So when we coding, please look at these parts carefully.