redhat sound card problems

I have Dell T5500 with Redhat installed,it have a tiny problem with it sound card.
when I get online to watch video,some of them have very low voice volume,event in visualized windows 7,especially the video recorded(not confirmed) from mac.I find following way can fix it

1) in console,run gstreamer-properties
2) in pop windows,changed Default output plugin from AutoDetect to ALSA(advanced Linux sound architecture).

CSS

CSS syntax:
1)p {color:red;text-align:center;} --- select(html element) and style
2)#para1
{
text-align:center;
color:red;
} --- is select and style
3).center {text-align:center;} ---class select and style
4)p.center {text-align:center;} --- html element's class select and style

how to use external style sheet: inside html "head" element put "link" element