Fonts tab in Tools : Options provides the following options:

• Interface font defines the font used in windows and dialog boxes throughout SuperMemo. To best see the impact of this options, click the button and change the font to the one you most like to work with. If you select a very large font SuperMemo will ignore your choice so that at least you were able to read the dialogs and change your setting back
• Question font defines the default font for texts components. This font will be used in all texts components where you do not specify a font yourself. Only answers components will use the font defined with Answer font below. Changing Question font will change the initial font used in editing HTML or RTF components. It will also affect all plain text components whose font is not specified. It will not change the appearance of HTML and RTF components edited in the past. Whenever SuperMemo is not sure which font to use, it will use Question font in various circumstances. Changing Question font will affect all plain text components were. 
• Answer font defines the default font used in texts components serving as answers to questions. It will be used for all textual answers unless you specifically request another font is used. If you change Answer font, answers of plain text components that do not specify the font will also change through your collection. This will not affect answers edited as HTML or RTF
• Use question and answer fonts in HTML: This option, when checked, makes sure that each time you start editing HTML text, the fonts specified at Question font and Answer font are used by default. You can uncheck this box if you want to save space and leave HTML texts unformatted whenever possible (you can use Internet Explorer to determine the default font used in HTML components)
• Contents font defines the default font used in the contents window. This font will also be used to display element titles in registries
• Highlight font defines the font used to highlight texts in incremental reading (e.g. with the highlighter icon on the Read toolbar)

There are four basic font options on the Text submenu of the component menu in all text components.

• Edit font allows you to edit the currently used font in a text component. In HTML and RTF components, the modified font will only affect the current selection. In other components, the font in the entire text will change. In addition, the font in the currently used template will be modified, as well as the currently linked registry font (if any)

• New font makes it possible to define a new font, add it to the font registry for later use (see: Search : Other registries : Font). After the new font is defined it is applied to the current selection in rich text components or to the whole text in plain text components

• Link font can be used to reuse a font previously stored in the font registry 

• Default font can be used to detach a registry font from the current component and the current template (if any). This, for example, will make the modified template use Question font and Answer font as defined in Tools : Options : Fonts (see above)

RTF and HTML components can use either formatted text with many fonts or space-saving plain text. To convert the text in HTML or RTF components to plain text use Text : Plain text on the component menu (e.g. press Ctrl+Shift+F12). To change the default font used in unformatted plain text in your HTML components, change the setting in your Internet Explorer (Tools : Internet Options : Fonts). Once you modify fonts in unformatted text in HTML components, it will be saved as HTML again