Hi,
Mozilla isn't uplevel browser by default (ASP.NET works for all browsers but how it is configured to render for them, is very different thing). To get browser detections work bit better, you need to add something as follows to web.config (inside <system.web> tags).
******
<browserCaps>
<!--NETSCAPE 6 ja 7 //-->
<case match="^Mozilla/5\.0 \([^)]*\) (Gecko/[-\d]+ )?Netscape[6|7]/(?'version'(?'major'\d+)(?'minor'\.\d+)(?'letters'\w*)).*">
tagwriter=System.Web.UI.HtmlTextWriter
browser=Netscape
version=${version}
majorversion=${major}
minorversion=${minor}
frames=true
tables=true
cookies=true
javascript=true
javaapplets=true
ecmascriptversion=1.5
w3cdomversion=1.0
css1=true
css2=true
xml=true
<filter match="^b" with="${letters}">
beta=true
</filter>
</case>
<!-- MOZILLA //-->
<case match="^Mozilla/(?'version'(?'major'\d+)(?'minor'\.\d+)(?'letters'\w*))..*">
<case match="^[5-9]\." with="${version}">
tagwriter=System.Web.UI.HtmlTextWriter
frames=true
tables=true
cookies=true
javascript=true
javaapplets=true
ecmascriptversion=1.5
w3cdomversion=1.0
css1=true
css2=true
xml=true
</case>
</case>
<!--
OPERA 5+
//-->
<case match="Opera[ /](?'version'(?'major'\d+)(?'minor'\.\d+)(?'letters'\w*))">
browser=Opera
version=${version}
majorversion=${major}
minorversion=${minor}
frames=true
tables=true
cookies=true
javascript=true
ecmascriptversion=1.1
<filter match="[4-9]" with="${major}">
ecmascriptversion=1.3
css1=true
css2=true
xml=true
<filter match="[5-9]" with="${major}">
tagwriter=System.Web.UI.HtmlTextWriter
w3cdomversion=1.0
</filter>
</filter>
<filter match="^b" with="${letters}">
beta=true
</filter>
</case>
</browserCaps>
****
For more exact explanation see this post at ASP.NEt Forums:
http://www.asp.net/Forums/ShowPost.aspx?tabindex=1&PostID=89874