To use all the advanced features of Crawler, a modern, fully capable web browser is required. It has to support frames and Javascript/DOM. If your browser doesn't support these, or if you disable those features in your browser, you won't be able to use Crawler webmail application.
Browsers that are fully supported:
MS Internet Explorer for Windows, version 6 and higher
Firefox (any OS), version 1.0 and higher
Netscape, Mozilla, AOL, Camino, and other Gecko-based browsers (any OS)1)
1) Note #1: Gecko (Mozilla) kernel 1.3+ is required. Prior versions, pre-release, alpha and beta versions are not supported. The Crawler applications could work here, though.
2) Note #2: These browsers fit the requirements, but there may be bugs that can cause the application not function properly.