argument of webservice

[Mr. x]

Hello,
I have tried to pass a string parameter to webservice like this :

On client side (javascript) :
var iCallID ;
....
var s
s = "<abc></ab";
iCallD = service.myfuncs.callService("myfunc1", s);

and on the server side (web-service - VB) :

<WebMethod()> Public Function myfunc1(my_str as string) as Integer
return(0)
end function


What I get by sending the specific string : "<abc></ab", is the following
error :

System.Web.Services.Protocols.SoapException : Server was unable to read
request

System.InvalidOperationException : There is an error in Xml document. the
abc start tag doesn't match the end tag of ab ...

I just want to pass a string, without any check.

1) What are the pros that Web-service check the validity of a parameter
string ? - Can this check be ignored by web-service, and just pass the
string as is ?
2) For String parameter - is there any limit to size of the string.
3) Can I pass Hebrew xml as a string ?
4) question 3 is like this : Can I pass xml string with header ? i.e : <?xml
version = "1.0" encoding = "windows-1255" ?> ? ...

Thanks