problem in understandin the code

[smyle khanna]

i have got a program to check email validation in java script,
since the function is small i want 2 implement in my program,but i cant undertsnad its workin
i would really appreciate if any1 could xplain me abt this code
wht does this line within the if braces mean?
thanks in advance.
Smyle

Now check if email is valid 
if (!(/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/.test(document.user.emailid.value))) {
alert("The email you entered is not a valid email address.");
//document.user.emailid();
return false;
}  

[Eric Pascarello]

All of the funky code is a regular expression.
what it does is try to match characters with the test.
basically it is saying
/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/
match any word/number/peroid or Hyphen then word/number
then match the @ symbol
{2,3} means has to be 2 to 3 characters
Do a search on google for reg exp syntax and it should explain it better.