When moving content from an existing CMS into Tridion, I have run across
<style> blocks in the RTF fields which the Tridion RTF strips out. Is there a way to prevent this?
<style> elements are officially not allowed in an HTML body element, I think the
TcmXhtml.Config isn't going to help you (as you confirmed by trying already).
So the best solution I can give you (it will mean extra work) is to see if you can split the RTF content up in two parts for the migration:
Strip out the
<style>tags (by means of XSLT for example) and add the remainder in the RTF field.
Copy the contents of the
<style>tag(s) to a separate field in the Component (plain text field) and in your Template you can decide whether to place it back in an (illegal ;o)
<style>tag in the body of your HTML, or if you move it up to the head or even in a CSS file (the latter is best but will probably be most work).
As nuno answered it here : https://stackoverflow.com/questions/9613598/how-to-add-custom-tags-to-rich-text-field-in-sdl-tridion
There is a file named TcmXhtml.Config under [Tridion]\web\WebUI\Core\Controls\FormatArea\TcmXhtml, where the rtf supported tags are defined. please check if your tag is there and if not present add it.