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>

因为validateRequest默认值为true。只要设为false即可。