FYI, the warning message isn't 'bogus' at least not in this case... for various security reasons it's better to always enclose the {param} tags in double quotes rather then single quotes... while I highly doubt anyone will have a problem the following codes will not display the error and is technically a bit safer. (I swapped the single and double quotes):
Code:
<img src="{param}" width="200" height="150" ondblclick='this.src="{param}";this.height=450;this.width=600' onclick='this.src="{param}";this.height=150;this.width=200' align="left" hspace="10">
Also I'm not sure what the purpose of "<!{param}>" is- I don't know what it does and it seems to work fine for me without it.