Form Validation (Java)

I am very new to JAVA but have some experience in HTML. For learning experience, I simply want to validate a form. Would really appreciate your advice and your example. If possible, the script with comments so I know what is going on.

Here is my form:
<FORM METHOD="POST"
ACTION="mailto:[email protected]"
ENCTYPE="text/plain"
onSubmit="return valid(this);">

<strong>Your Email:</strong>
<input type="text" name="email">
<br>
<strong>Date:</strong>
<input type="text" name="date">
<br>
<strong>Time:</strong>
<input type="text" name="time">
<strong><br>
<br>
Please write the issue:</strong><br>
<textarea name="problem" COLS="80" ROWS="10"></textarea>
<br>
<br>
<INPUT TYPE="submit" VALUE="Submit">
</FORM>

The validation:
- Email address = the email address has an "@" and a "." following the "@" sign.
- Date = date is entered in the format 03/15/2007
- Time = e.g. in the form 3:35 PM or 11:02 AM
- Please write the issue = problem description is at least 2 characters long

<SCRIPT> LANGUAGE="JavaScript"> I believe is a good start.. (help please).. Any example of a very simple script, with comments if possible. I checked the script on many sites, and I am still confused with the code. Thanks for any help..