My name is Bozhidar Ruzhenov and I am one of the Front-end Developers responsible for the Telerik RandControls HTML/CSS markup.
Our willingness is to use CSS3 and to create rounded corners and shadows easy and simple, but unfortunately it will not be possible until Internet Explorer versions 6, 7 and 8 have large part in the browser market.
A lot of our customers are big corporations that are using internal applications and Internet Explorer 6. So, when we should deal even with so pre-historic browser, what about for Internet Explorer 7 and 8? I do not believe that they will disappear soon and will be replaced by Internet Explorer 9, which is expected to have really good support for CSS3. In that case, we should still use the old way to create rounded corners and shadows with images and extra markup. For me personally, it will be much more easier to use CSS3 and to create shadows and rounded corners for all the Telerik Skins just for a couple of hours instead to create a lot of sprites and extra markup.
If we decide to skip IE browsers and to apply some CSS3 techniques, it will generate a lot of support, as we declare that out products are cross-browser compatible.
In our control - RadFormDecorator for the text inputs we are using CSS3 for the rounded corners - check rfdRoundedCorners class. Of course it works in Firefox, Opera and WebKit browsers. For IE we are using different extra markup. In some cases that generates a lot of support and we have to explain why in one browser the code looks one way and in the other - totally different.
I hope you understand our statement, we know we should try to find the perfect balance between the new techniques and all browsers, which now is predetermined by the large browser market of IE 6, 7 and 8.
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.