The optimal solution at the moment is to use:
selector { -webkit-border-radius: 50px; -moz-border-radius: 50px; border-radius: 50px; }
This will work in all "modern" browsers, including IE9, see: http://caniuse.com/#search=border-radius
To date, the best solution for older versions of IE is to use CSS3 PIE :
PIE makes Internet Explorer 6-8 capable of providing some of the most useful CSS3 styling features.
PIE currently has full or partial support for the following CSS3 features:
• border-radius
• box-shadow
• border-image
• multiple background images
• linear gradient as background image
As you can see, you also get support for more CSS3 eye candy
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