[jQuery] Selector with Pipe (|) character not working

I am trying to select an element with with ID which have pipe
character (|)....
i found that its not working
CODE--HTML
<input type ="text" id="firstName|1" name="firstName|1"/>
CODE-SCRIPT
alert($("#firstname|1").val() );
and output is "undefined"..............................
Works well if i remove pipe
Please help me..is it a bug or "feature"