Can somebody write some Javascript for me?

Essentially, you want code for browser detection. Another helpful page.

 

I would try and do the browser redirect in PHP if possible (less load on the client).

Also what features is he wanting? You could easily do shadows, rounded corners, etc as images.

Also, with a strict doctype IE7 should render pretty closely to standard browsers. You just gotta watch white space bugs and z-index bugs.

If a client of mine wanted an IE6 compatible site I'd probably slice it into tables and just pull the content in with PHP includes.

 

If you find the only differences necessary are CSS related, and noting anyone can disable Javascript and break your site, consider using the MSIE conditional CSS hack or the use of !important in your style attributes.

Details about the the CSS hack method are found here.
Details about the use of !important are found here.

Example CSS hack in your HTML:

HTML:

<!--[if IE 6]>
Special instructions for IE 6 here -- i.e. load a different stylesheet
<![endif]-->

Example of !important for special styling for MSIE6 or lower:

HTML:

p {
   background: green !important; /* Major browsers other than IE 6 and below respect the importance immediately */
   background: red; /* IE 6 and below use this value instead, even though the above was marked as important */
}

And finally, consider calling reset.css before any other styles which helps with common cross-browser CSS problems including this one. Plenty versions out there.

-jim