What version of mod_proxy_html are you using? You must have more code than you posted or are you using an old version of mod_proxy_html?
In the distribution I have, there's a file called proxy_html.conf which contains all the following example configuration. Do you not have this in yours?
ProxyHTMLLinks a href
ProxyHTMLLinks area href
ProxyHTMLLinks link href
ProxyHTMLLinks img src longdesc usemap
ProxyHTMLLinks object classid codebase data usemap
ProxyHTMLLinks q cite
ProxyHTMLLinks blockquote cite
ProxyHTMLLinks ins cite
ProxyHTMLLinks del cite
ProxyHTMLLinks form action
ProxyHTMLLinks input src usemap
ProxyHTMLLinks head profile
ProxyHTMLLinks base href
ProxyHTMLLinks script src for
# To support scripting events (with ProxyHTMLExtended On),
# you'll need to declare them too.
ProxyHTMLEvents onclick ondblclick onmousedown onmouseup \
onmouseover onmousemove onmouseout onkeypress \
onkeydown onkeyup onfocus onblur onload \
onunload onsubmit onreset onselect onchange
# If you need to support legacy (pre-1998, aka "transitional") HTML or XHTML,
# you'll need to uncomment the following deprecated link attributes.
# Note that these are enabled in earlier mod_proxy_html versions
#
# ProxyHTMLLinks frame src longdesc
# ProxyHTMLLinks iframe src longdesc
# ProxyHTMLLinks body background
# ProxyHTMLLinks applet codebase
I've just tested mod_proxy_html and it seems to pass through the IE7 code you supplied fine with me.
Phil.