Quick Javascript Form Validation

I'm trying to protect a form from being submitted by the website it resides on. I'm using the following code, but this just stops the form submitting if '@email.com' is in the form field. How can I say 'if this field contains @email.com then do not submit'?

Whilst we are at it, I also need to do the same with php if anyone also knows this?

Code:
if(value.itech03.value == "@itech.com") {
alert("Message here.");
value.itech03.focus();
value.itech03.select();
return false;
}