Widget fonts

the widget title might (but not always) have the CSS class .widget-title; try to use a browser inspection tool to be sure; then edit the stylesheet of your theme, and either locate any styles which might already be there to format the widget title’s font size, or add a new one.

http://codex.ww.wp.xz.cn/Forum_Welcome#Include_as_much_information_as_possible

Weaver theme has really good support from the developer here:

http://weavertheme.com/forum/