FCK editor parses the entered HTML code prior to sending it via form submission. It converts the code in a way it finds to be best suitable for HTML standard. By that standard, <STYLE> tag goes into HEAD of the document.
If you wish FCK not to parse the content prior to submitting, then: - click the code button - paste the code - submit the form without returning to editor view
Otherwise you can modify a FCK editor which is located in /admin/functions/editor/ folder. I
Due to various webmail filters imposed on CSS in HTML documents, it is always better to avoid using <STYLE> tags completely, to use inline style declarations within HTML tags ("style" attribute).