i have convert theducks suggestion into my simple html:
<div style="margin: 1em 2em; padding: 20px; background-color:C1C3C3">
<p style= "margin: 0.5em 0; color: red">text here</p>
</div>
but.... 1) i don't want any text, only simple color box only only for an aesthetic factor, then <p>text</p> it is not necessary.
2) no box appears! it's better my solution at post#3...