Fatal's Journal

1. Make a widget. This step may seem obvious, but the first and most important step is actually creating a working widget.

1. Use standards
   Check if you widgets actually have valid HTML and CSS. There are no more excuses about crappy hacks for Internet Explorer.
   
2. Use modern standards
   Check out standards that Opera already supports. Use modern standards like SVG, WebForms 2, HTML 5 (canvas), CSS 2.1 and 3 (selectors), XSLT, XPath, etc. It can make shorter development time and improve user experience.
   
3. Check accesibility
   Create widget as it will be standard web page. Care about disabled people - provide alt attributes to images, use labels for form fields, check if your colors are contrast enough, etc.