For a discussion on the shortcomings see Usage share of web browsers.

Internet Explorer still commands a large percentage of Usage share according to the Usage share of web browsers.

The usage share of web browsers is the proportion, often expressed as a percentage, of visitors to a group of websites that use a particular web browser.

A detailed overview of the support regarding the most popular browsers (as a percentage of market share as of September 2012, taken from Usage share of web browsers):

Andreessen, the leader of the Mosaic team at NCSA, soon started his own company, named Netscape, and released the Mosaic-influenced Netscape Navigator in 1994, which quickly became the world's most popular browser, accounting for 90% of all web use at its peak (see usage share of web browsers).