 <p>Think about the wasy jQuery handles selectors:</p> <pre><code># denotes an id: '#id' . denotes a class: '.class' : denotes a pseudo class: ':pseudo_class' </code></pre> <p>So when your doing your selection it is expanding to:</p> <pre><code>$("#j_idt23:txtNumber") </code></pre> <p>Meaning find an element with id = 'j_idt23' and pseudo class 'txtNumber' but txtNumber isnt a valid pseudo class, and jQuery is confused.</p> <p>Change it to something like <code>"j_idt23_txtNumber"</code></p>