Quoting MSDN on the CSS "clip" property:

As of Internet Explorer 8, the required syntax of the clip attribute is identical to that specified in the Cascading Style Sheets (CSS), Level 2 Revision 1 (CSS2.1) specification; that is, commas are now required between the parameters of the rect() value.
...
In Internet Explorer 7 and earlier (and in Internet Explorer 8 or later in IE7 mode, EmulateIE7 mode, or IE5 mode), the commas should be omitted.

I see a few options:

• Giving both rules, hoping that the browsers will just ignore one they can't parse (and not revert to no clipping) - untested
• Use Conditional Comments to use a "ie7fixes.css" file (works)
• Do not use clipping (the most commonly used solution)
• Ignore the existance of Internet Exploder 7 and just follow the CSS 2.1 standard (that's the way it should be)