The font size of the value of an text area is not choosable in the options of a show instance layout. Whatever I input as a font size, the font size remains the same.

Color, bold etc is working.

Hello. Please clarify, your question relates to our templates, or to CCK?

I use CCK with the blank template. it happens in show instance layout in the styling options for the value of a text_area field

Hello. I noticed that you are using an editor to enter textarea fields. When you use the editor, it gives precedence to the settings that were entered through the editor. In this case, we see the following font information in the editor: size 12pt.
And it is this size is displayed on the site, as it is specified in the HTML markup lower than the size you set in the field settings. So to change the size, you need to change it in the editor.

I tried to switch off my text editor. Nothing changed.
I saw in the source code of my browser the font-size has always the same value as I had put in to the styling option.
There must be another reason.
Other text area fields also get sized correctly as I put the size into the style option font-size field.

Okay. Maybe later I will try to find out the reason. I will check now the raw data in the database

No I found it out what is the reason:
In style.css file I defined the p tag with a font-size "18".
If I write now in an text area of cck, the paragraph gets automatically the font-size 18 because there is a <p></p> tag.
The font-size which I put into the option style of an text area field inCCK is getting overwritten bei the p tag in the style.css file.

I know the original blank template has not defined a font-size for the p tag. I added it some month ago because I needed bigger fonts for my joomla articles.
Unfortunately in the OS templates one cannot edit or choose a font-size for joomla articles. I use also the native joomla articles on the website and not only the os cck system.

As a temporary solution I don't use the enter key anymore in text area fields. Instead I use the shift-enter key which sets a <br> tag. But this is not satisfactory in the long run.