concatenating user input and special characters

Hello again,
 
I need to add XLink information to my xforms instance data like 
 
<xforms:instance>
    ...
    <link xlink:href="#website"/>
    ...
</xforms:instance>
 
whereas the "website"-part should be the input of the user. How can I attach the "#" character to this information? 
 
wbr,
Roman