I have been trying to change the border setting for multiple selection drop down menu in ASP.NET. After a bit of testing, I realised that all the style sheet code was not being rendered to the drop down list, when viewed in Internet Explorer. Mozilla FireFox was good enough, and even Safari, did help me out, but it was IE that did not budge! Then googling it gave me following explanation why IE did not work as expected.
"For historical reasons, some form-elements are elements from the operating system’s GUI. Rendering of these elements differs from browser to browser. Most of the browser, take into consideration the style sheet information about the element, and if not present renders the default properties from the OS’s GUI. For IE unfortunately these elements are <select>, <checkbox> and <radio>."