potentially dangerous request.form asmx web service

I was having this issue while using http post protocol on a web service (asmx) .

i was pasing xml string to the browser and on local network it worked fine on windows 2003 server (Developed on visual studio 2008)

application was moved to windows server 2008 and on .net framework 3.5 on deployment server .

i came to know the following solution but was not allowing me to add this in web.config because of the reason , i was using visual studio 2008 for updating web.config

The solution was to update the project to visual studio 2010 and to add the following line in web.config file
<
httpRuntime requestValidationMode="2.0"/>