HTML Attribute for <INPUT ...>
MAXLENGTH =integer

MAXLENGTH sets the maximum number of characters for text or password fields. 

<FORM ACTION="/cgi-bin/mycgi.pl">

account ID: <INPUT TYPE=TEXT NAME="accountID" MAXLENGTH=4><BR>
password: <INPUT TYPE=PASSWORD NAME="password" MAXLENGTH=8>

<P><INPUT TYPE=SUBMIT VALUE="submit">
</FORM>

gives us this form:

account ID:
password:

(Form is not live)

<INPUT CHECKED> >