look in the skin1/customer/main/navigation.tpl file
Since there is no style associated with it, it is using the default style setting in the skin1.css file.
You could either 1) add a new style in the css file and then define the class in the navigation file where you see the following code {%page.index%}...
Code:
{%page.index%}
</td>
{else}
<td width=17 background="{$ImagesDir}/page.gif" align=center>
{%page.index%}
Or you could hardcode the font settings instead of using the skin1.css file like below
hope this helps.