Xml declaration should precede all document content

The error message "XML declaration should precede all document content" means that there is some content in your XML file before the XML declaration. The XML declaration should always be the first line in an XML file, before any other content.

To fix this issue, move the XML declaration (usually starts with `<?xml version="1.0" encoding="utf-8"?>`) to the very beginning of your XML file, before any other content. Make sure that there are no characters or whitespace before the XML declaration.

Here is an example of what your XML file should look like:

<?xml version="1.0" encoding="utf-8"?>
<root>
    <element1>...</element1>
    <element2>...</element2>
    ...
</root>

If you are using an XML editor or IDE, it may have an option to automatically insert the XML declaration at the beginning of the file.