Are you sure you want to go the captcha route? Why not ask for an email address and email them the access code? Emailing the access code eliminates problems for blind users because we can assume they have a way to read/hear their email. Plus, you then have a way to track users and contact them. If you want your service to be anonymous, then that might be a bad thing.
On the other hand, bots could generate a million fake accounts by using a million self-generated email addresses, but it that really what you're worried about? Is your registration for a service that bots would want? Does it include giving users an email address or something?
Hope that helps!
Are you posting in the right place? Check out Where do I post X? to know for sure.
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
Want more info? How to link or
or How to display code and escape characters
are good places to start.