JSF 2 + Richfaces 4 + Seam

In order to overwrite the default richfaces 4 ecss styles, from the document(https://docs.jboss.org/richfaces/latest/Developer_Guide/en-US/html_single/#sect-Developer_Guide-RichFaces_overview-Restrictions). You need to put it to <h:body> section:

JSF does render resource links (stylesheets, scripts) in order of occurrence, thus if you add &lt;h:outputStylesheet&gt; to the &lt;h:head&gt;section, JSF will render it before the RichFaces resource links (dependencies of RichFaces components). To be able to overwrite RichFaces stylesheets and re-use RichFaces JavaScript implementation, you need to render &lt;h:outputStylesheet&gt; to the &lt;h:body&gt;section (safe solution is to place it on the end of the section; however to keep readability, you can use start of the section).