A degradable font is just a list of different font types in which you would like some text to be rendered. When a visitor views your web page, their browser searches through the font list, looking for the first installed font on their computer. Then the text is rendered in this font type.
It is necessary to have a list of fonts, in case the visitor viewing your webpage does not have one or more of the fonts you would like rendered installed on their computer.
Do one of the following:
On the Format menu, select Font.
Click the Font button on the Format toolbar:
Press F2.
Click 
in the Format Font dialog.
The Font Group drop-down
list is used to specify a group of alternative fonts that a web
browser can use if the primary font is not available. Click 
to create a new font group. (Clicking 
allows you to delete the selected font group.)
The Available Fonts panel
displays the list of fonts available on your system. Select a font on
this list and click on 
to add the font to your new font group. If you wish to add a font to
the Font Group that is not on this list, type the name of the font in
the drop-down list field below and then press <Return>
or <Enter> on your
keyboard. (Clicking 
allows you to delete the selected font.)
Repeat step 2 for any other fonts you wish to add to your font group.
You can click 
and 
to move different fonts you have selected in the font group up and
down the list. If a primary font is not available then a web-browser
will be able to use this list of alternative fonts in the order specified.
Click <OK> to save your new font group.
Use either the Format Font or the Format Paragraph dialogs to apply formatting to selected text (or a paragraph).
When selecting a font from the drop down font list, your font sets are listed at the top.
An example of selecting a font list.