javascript for SELECT and COPY

I tried the following to select/highlight and copy the textarea:

<input style="float: left; background-color: #B5A26F; border-color: #98A9A9; 
width: 150px; font-weight: bold; color: #FFFFFF;" type="button" value="Select All" 
onClick="javascript:document.getElementById('forum_quote').focus(); 
document.getElementById('forum_quote').select();" />

Code (markup):

I'm getting this error:

 

Is there HTML element with id=forum_quote