my css setting is overwrited by UI

I am using JQuery accordion, but it always overwrite my css setting.

For example, in my page, I set font to sans-serif. I add accordion plugin into my project, then this font will be erased, it will cause whole page style is not consistent. How can I keep my css setting?

I know the problem is in jquery-ui-1.7.1.custom.css (redmond), which part I should change ?

Thanks.