I need to edit a full html page with ckeditor

You will need to set the fullPage configuration option to true.

config.fullPage = true;

See also the "Full page support" sample.

No need to offend anyone but everyone seems to be very bad at explaining things and are just simply saying  "config.fullPage = true;" but no one is explaning or saying where exactly and here is how you do it.

in this code snippet below:

"CKEDITOR.replace( 'CKEditor' );"  

replace that with this code below and it should work:

CKEDITOR.replace( 'CKEditor', {
    fullPage: true,
    allowedContent: true
});

than it should look like this:

<center>
        <form>
            <textarea name="editor1" id="CKEditor" rows="10" cols="80">
            </textarea>
            <script>
                // Replace the <textarea id="editor1"> with a CKEditor
                // instance, using default configuration.
                CKEDITOR.replace( 'CKEditor' );
</script>
        </form>
</center>

[PROBLEM SOLVED]

Hi Gameslayer,

it's great that you want to help, however:

1. CKEditor has extensive documentation and samples. These are the first places where every developer trying to do something with software that (s)he has downloaded should head, to learn how the software works and how to customize it.
2. This is why it makes no sense to post "complete" solutions on the forum. E.g. you are using the CKEDITOR.replace() method to create the editor, but others may want to use an alternative method to create a classic editor or use inline editing, so your method won't work for them and you make it sound as if it was an universal solution.
3. Last but not least, I would still say it makes more sense to send the user to a working sample, with the exact same snippet that you copied, and the full source code to examine than just paste the snippet here...