Internet Explorer supports, to some degree, a number of standardized technologies, but has numerous implementation gaps and conformance failures—some minor, some not—that have led to criticism from an increasing number of developers. The increase is attributable, in large part, to the fact that competing browsers that offer relatively thorough, standards-compliant implementations are becoming more widely used.
Internet Explorer's ubiquity, in spite of its inferiority in this area, frustrates developers who want to write standards-compliant, cross-browser code and the advanced functionality it provides, because they are often stuck coding pages around Internet Explorer's bugs, proprietary featureset, and missing standards support instead.
Developers must work with the technology supported across all browsers for cross-platform development, and Internet Explorer is often criticized for being technically inferior. These include supporting fewer or wrongly interpreting more CSS, HTML, and DOM features than Firefox or Opera and not having native XHTML support. As a result of these, it does not pass the Acid2 test, a test case designed by the Web Standards Project to verify CSS compliance.