HOW TO achieve XHTML compliance by changing existing HTML code in upper case to lower

Visual Studio neatly alerts you rightaway whenever you commit an XHTML indiscretion. But what if you have inherited an application from someone who is not Standards-savvy & the pages are messed up with green squigglies? A casual coder may hand-code HTML without bothering about the case. How do you correct all the HTML in upper case across multiple pages & make them XHTML compliant?

Select the HTML text in VS 2005/2008, right click and select "Format Selection". Sit back & watch while Visual Studio nicely arranges the code with proper indentation & converts the appropriate HTML tags in upper case to lower case.