This post is over a year old, some of this information may be out of date.
These days I get a lot of questions to change the font-family or font-size of a SharePoint 2010 site. As many of you will know you can easily change the font-family in the theme settings, but it will not be applied to all the elements.
The same count for changing the font sizes in SharePoint 2010. You simply cannot adjust the font size by only changing the font size value for the body element, and this is really frustrating.
SharePoint uses all kind of font size attribute values. It works with pt, px, em, and %. The combination of all the font size units makes it difficult to adjust the font size for the whole site.
Because of these problems/frustrations I started to map out all the font-family and **font-size **attributes that are used in the SharePoint 2010 stylesheets. For every CSS file, a copy will be made with the font-family and font-size references. Font size attributes are ordered in size and by unit.
A good reference for using font size units is the following: CSS Font-Size: em vs. px vs. pt vs. percent
New CSS Files: 08/08/2011
New CSS files are uploaded (calendarv4.css, datepickerv4.css, layouts.css, search.css, wiki.css).