You can change your text added in HTMl by clicking on Edit Text link in Edit mode, shich will take you to an edit window having Rich text box, where user can format text as per requirement.

Suppose you are usiing Html module in your own module then to apply css you need to create a css file and add the css class to the html object using
objHtml.Attributes.add("class", "classname")


Sibabrata Dash
Mindfire Solutions
www.mindfiresolutions.com

We are usually creating css file for apllying style for the object present inside in our custom module. For that we can create the css file inside
>./Desktop Modules/Custom Module Name folder/


Sibabrata Dash   
www.mindfiresolutions.com