This is an Idea that I have heard bouncing around the web for a while now. I read a very insightful article on hacification which strengthened the argument considerably.
Good Reasoning
One of the best reasons for charging extra is to enable the client to recognize the time and effort that goes into fully browser complaint websites, it takes blood sweat and tears go get compatibility just right. So charging for this as an extra service is not entirely unreasonable, after all this comes separate to the time spent designing and developing a websites look and functionality.
The truth is there has never been a de jure standard for browsing the web, which in my own opinion is one the webs greatest downfalls. Instead there is too much choice on how to navigate your way through. This has lead to a grey area when talking about web design. The assumption that a website should be viewable through any means is a fallacy, but no one has ever acknowledged this properly. The W3C have introduced standards and done a lot of very good work, but it means nothing when designers are still expected to cater for decrepit platforms such as IE6 & 7, after all lets face it Microsoft just don’t get web, They should stick to what they know, which is desktop applications. By its very means Windows messenger, and Windows Hotmail, is a complete cop out, when Im looking at my emails on my OSX im not opening my messages with a different operating system, but anyway that’s besides the point.
Problems with the Plan
As with any great suggestion there are flaws. The main concern I have is how well the argument stands up in the real world. Consider that you were sold a car, but told you could only drive it on motorways, as the wheels may fall off if you drove it on any other roads. You wouldnt stand for it, so is it acceptable in web? This is something I have thought about an awful lot, but something Im still not sure I could actually do. Perhaps it depends on the client and their requirements, the scale of the project also make a great impact. I would be interested to know what others thoughts are on this topic!?

1 Kelkyron 13/11/08
I agree that there should be an extra charge for old browser support…nowadays the most common browser according to [http://www.w3schools.com/browsers/browsers_stats.asp] is Firefox at 44%, IE7 at 26% IE6 at 20%. The point is the percentage for older browser is really small…but if it is a big project…i think the cost of that project can compensate for the time spent developing the site for older browser compatibility..
2 Derek Pennycuff 13/11/08
i think the key is to explain it to clients as a return on investment. it’s pretty easy to ensure basic functionality on anything from lynx up to modern browsers. but trying to get every rounded corner and ever enhanced feature to work in netscape 4 or IE5 (or even IE6) requires a lot more code and a lot more work. that costs more to build today and it costs more to maintain forever.
ok, my comment just got longer than your original post. i think i’ll turn it into a blog entry of my own.
3 Derek Pennycuff 05/12/08
Just wanted to let you know after I cut and pasted my response to this entry into Blogger, I got slammed with real work and it sat in draft mode for the past month. I finally got around to actually publishing it today.