Using double border - Page 1

Hello,

i have a problem with displaying a double border on an inline element in my PDF-File.

I'm using this css-command: border-bottom:5px double #000

The double border is displayed in the TinyMCE - Editor but not in the PDF-File.

I've recognized that double border in the Example is used on a Table-Element. But it is also possible on an Inline-Element ?

borders and advanced background are only worked on tables, td, th and div