Style specifications in Textile formatting are not applied in Redmine
In the original Textile formatting, you can freely specify styles by writing CSS properties (for example: {background:#ddd}.). However, in Redmine you can use only some properties, as a measure against XSS (cross-site scripting) attacks.
CSS properties that you can use in Textile in Redmine
background, border, color, float, font, height, margin, max-height, max-width, min-height, min-width, padding, text, width
What to do if you want to use all CSS properties
If the risk of XSS attacks is acceptable in your environment, you can enable style specifications by changing the source code.
In lib/redmine/wiki_formatting/textile/formatter.rb, change self.filter_styles=true to self.filter_styles=false and restart Redmine.

