You can set the styles inside the editor textbox by using external CSS files. UltimateEditor provides the
TextBoxCssFiles property to set the CSS file names.

You can use multiple CSS files by setting the TextBoxCssFiles property to a comma-delimited list of CSS file
paths as follows:

<kswc:UltimateEditor ID="UltimateEditor1" runat="server"
TextBoxCssFiles="/Karamasoft/UltimateEditor/v3.0/Demos/CS/Samples/Style/
ExternalCSSFiles/StyleSheet1.css, /Karamasoft/UltimateEditor/v3.0/Demos/
CS/Samples/Style/ExternalCSSFiles/StyleSheet2.css" />

You should use absolute paths (either full path starting with http prefix or / character) for your external CSS file
paths so that they can be reached from inside the editor content area.