There is a lot of push-back in industry for not supporting the Microsoft Internet Explorer browser, but I would argue that installing Mozilla Firefox is a fairly light weight requirement for using a specific web application.
I often look for commercially available software components to reduce development costs. Most of the systems that I write for customers run on a single server and have a modest number of users so reasonable licensing costs can be a lot cheaper than extra labor costs for devlopment. I have a wish-list for Firefox extensions for form input, inline rich text editors, spreadsheet components, etc. If developers of useful Firefox extensions had a larger market (i.e., lots of web sites and web applications standardized on Firefox) then the cost per component would go down, and everyone but Microsoft wins.