Html Forms

[fishwieght]

I am stuck.  I want to make someone input an email address when they fill out my contact form.  I am getting people putting there names and leaving me no way to contact them.  How can I make it so when a person pushes the submit button, if they dont put an email address or phone number down it will give them an error message? I use Dreamweaver. Thanks in advanced for all help, I need it!

[michaewlewis]

javascript.
Have the submit button run a script, before sending, that checks the fields to see if they're filled.
Search for "form validation javascript": http://search.yahoo.com/search?p=form+validation+javascript&ei=UTF-8&fr=moz2