'?' introduced when insert html string into varchar max column

Hi,
my application require me to save some HTML snippets into DB ( i am using SQL 2008 R2 express ) table which varchar max columns. A particular string is:
"...<span style='position:relative;top:3.0pt'> </span>..."
I wrote a program in c# which extract HTML snippets from the main html file. The program will create  a sqlcommand, pass in the html snippet as string into a stored procedure and execute the insert. In the C# program, the parameter of this field is declared as 'SqlDbType.VarChar' and in the stored procedure, this parameter is declared as 'varchar(max)'. I checked that just before the insert (eg. ExecuteNonQuery()) the html string is still fine ( a blank space in between the span tags ). 
However, when i checked the record in DB, i found that a '?' has replaced the blank between the span tags. 
"...<span style='position:relative;top:3.0pt'>?</span>..."
is there any ...