A potentially dangerous Request.Form value was detected from the client (txtTest=).
错误提示：
A potentially dangerous Request.Form value was detected from the client
(txtTest="<b>").
由于在.net中，Request时出现有HTML或Javascript等字符串时，系统会认为是危
险性值。立马报错。
解决方案一：
在.aspx文件头中加入这句：
<%@ Page validateRequest="false" %>
解决方案二：
修改web.config文件:
<configuration>
<system.web>
<pages validateRequest="false" />
</system.web>
</configuration>