Ms Swati constructed a static website for their customer. She received hundreds of complaints within 1 hour of launching. All the complaints were related to mess-up design. She was the victim of compatibility issue of java script & CSS across many browsers and screen resolution.
Better solution is to use GIF images instead of PNG. Because their transparency is preserved across browsers. Or you can go for 2 color images for rounded corners. See the sample in side.
You can make images for corners using any image editor. Otherwise use online service for the same.