For some reason Chrome thinks the page in the iframe is encoded as Simplified Chinese (UTF-16LE). Try putting a meta charset tag on the page(s) in the iframe, ex:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<HEAD>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<LINK REL="stylesheet" HREF="style3.css" TYPE="text/css">
</HEAD>
<BODY>
<div style="margin-top: 30px; margin-bottom: 2em; text-align: center; font-size: 90%">
<p style="margin-bottom: 50px">
Choose one of the cards below, and remember it.
</p>
<img src="cardsb.gif" height="176" width="600" alt="card trick">
<p class="solution">
<a href="cards2.htm">CONTINUE</a>
</p>
</div>
</BODY>
The browser cache may need to be cleared and/or the page refreshed to see changes.
If that doesn't work, you will need to configure the default encoding of the server or have your host do it for you. It should not be UTF-16, probably UTF-8, but since you seem to favor ISO-8859-1, perhaps that would be best for your site.