Browser

This is the client software that displays (interprets) the HTML code it receives from a web server.

All browsers work slightly different and interpret the HTML code slightly differently if the code was developed exclusively for a specific browser. Today the two main browsers are Microsoft Internet Explorer and Firefox.

Firefox is a web developers preferred choice of browser as Mozilla (who owns Firefox) have tried to create, what is understood to be, the standard in Browser technology. Firefox build on existing technology so when an update is issued it is likely that websites built for viewing in Firefox will still display accurately.

Unfortunately the developers behind Internet Explorer (IE) do not take a similar approach. Microsoft often change the way Internet Explorer interprets HTML in each and every revision. 

The most likely reason for this is due to Internet Explorer being an integral part of the Windows operating environment and it not being a stand alone web browser. This means that as Windows is expanded and updated Internet Explorer also has to be.