"allowfullscreen" is not a member of a group specified for any attribute.
This simply means that the HTML tag on which you are trying to use the allowfullscreen attribute does not permit the allowfullscreen attribute. To resolve this:
- Make sure you are using the allowfullscreen attribute on the iframe tag. Other tags are most likely not valid.
- Make sure you declare your document as using HTML 5. This means that the first line in your HTML document should read: <!DOCTYPE html>
Invalid error: Attribute allowfullscreen not allowed on element iframe at this point
Similar to the previous error, you'll want to make sure that your document is declared as an HTML 5 document. If you are still using HTML 4 or another version of a markup language, then you may receive this error.
Simply make sure that the first line in your document is <!DOCTYPE html>, and this will ensure that your entire document is in HTML 5 format.
There is no attribute "allowfullscreen".
In this case, make sure you are using the allowfullscreen attribute in an HTML 5 document. Inserting <!DOCTYPE html> as the first line should do the trick. The allowfullscreen attribute is most likely not valid in any other document types.