It is likely that you have made edits to the style using the rich text editor. Any formatting applied in the rich text editor over-rides the formatting made to your style sheet.
Ideally you should universally set your default font-size font-face, and colours from the My Web site page - select Fonts for the face and size and set your text colours from Colours and Backgrounds. After doing so, ALL the text on your site will automatically be set to your selections, even words like on your Contact page which cannot be controlled via the rich text editor. To reset the paragraphs you have styled within the rich text editor use the "Remove Format" tool in the rich text editor with the text selected.