html5 css selector rules cannot start with digit code example
Example: dom ids have numbers
//as long as it starts with a letter
<div id="Az1_2.3:0-9">is an acceptable dom id</div>
//and in any combination of the above.
//as long as it starts with a letter
<div id="Az1_2.3:0-9">is an acceptable dom id</div>
//and in any combination of the above.