Last week Bill Gates got the interoperability religion. Allegedly - given Microsoft's long and sometimes less than constructive history in the field of interoperability, a certain amount of scepticism is perhaps appropriate. Hakon Lie, Chief Technology Officer of long-standing Microsoft competitor Opera Software, welcomes Gates' new-found enthusiasm for interoperability, but in the following response to Gates, has just a few suggestions about what Microsoft might do to actually achieve it. So, Mr. Gates, writes Hakon Lie, you say you believe in interoperability. Then why, pray tell, doesn't the web page of your interoperability communiqu� conform to the HTML4 standard as it claims to? Why does the W3C validator diagnose 126 errors on your page? You say you believe in interoperability. Then why is your document served in different versions to different browsers? Why does your server sniff out the Opera browser and send it different style sheets from the ones you send to Microsoft's own Internet Explorer (WinIE)? As a result, Opera renders the page differently. You say you believe in interoperability. Why does the Hotmail service deny Opera access to the same scripts as Microsoft's own browser? As a result, Opera users can't delete junk mail.