Does IE7 have a "developer mode" or plugin like Firefox/Chrome/Safari?

Possible Duplicate:
Debugging JavaScript in IE7

Firefox has Web Developer plugin and Firebug for troubleshooting html/css/javascript issues. Google Chrome and Safari have a very similar console and right-click options for "Inspect Element".

Does IE7 have anything similar for troubleshooting layout/html/css issues?

Yes - The Internet Explorer Developer Toolbar

Download details: Internet Explorer Developer Toolbar

You can also use Firebug Lite, wich works on IE, Opera and Safari.

It's a Javascript implementation that you can load with a simple bookmarklet.

As SO doesn't allow Javascript, here is the bookmarklet source code (just copy paste to your browser location bar (always make sure it's safe before executing random javascript (In any case check the first link)))

javascript:var%20firebug=document.createElement('script');firebug.setAttribute('src','http://getfirebug.com/releases/lite/1.2/firebug-lite-compressed.js');document.body.appendChild(firebug);(function(){if(window.firebug.version){firebug.init();}else{setTimeout(arguments.callee);}})();void(firebug);

Firebug Lite supports all basic commands of Firebug.