<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML> <html> <head> <script type="text/javascript"> function validate_email(field,alerttxt) { with (field) { apos=value.indexOf("@") dotpos=value.lastIndexOf(".") if (apos<1||dotpos-apos<2) {alert(alerttxt);return false} else {return true} } } function validate_form(thisform) { with (thisform) { if (validate_email(email,"Not a valid e-mail address!")==false) {email.focus();return false} } } </script> </head> <body> <form action="submitpage.htm"onsubmit="return validate_form(this);" method="post"> Email: <input type="text" name="email" size="30"> <input type="submit" value="Submit"> </form> </body> </HTML>
原文：http://www.cnblogs.com/the-wang/p/7511093.html