CSS not working on id on jsp

On my jsp page outputText tag when I use id, my css style sheet doesn't pick up on it, but when I change it to class it works.

jsp:

<h:outputText id="namelabel" value="Name:" /> 

css:

#namelabel {

    font-weight: bold;
}

When I used the id for the parent <h:form> it does make the font bold for that whole form, so I don't understand the difference, could anyone explain? Feel like im missing something obvious..

At the moment its not a problem, but Im also wondering for future reference if I wanted to give unique CSS rules to that particular outputText, or would I just add another class rule to it? I suppose Im asking about best practice here too.

Im also using ajax, netbeans and deploying to GlassFish.