I have content that appears within a corporate website inside an iframe. Several departments contribute their own CSS files to manage the overall UI and design.My problem is that they may use selectors for elements like td (for instance), without notice. Of course that will affect my own content in the frame unless I add a class to every td. I'm just using td as an example: the generic style for any element could change without notice.Is there any method/convention/practice I can use to protect my own styling? 
protecting css selectors on large website
css
Include reset.css after loading all your CSS files:html {    color: #000;    background: #FFF;}body,div,dl,dt,dd,ul,ol,li,h1,h2,h3,h4,h5,h6,pre,code,form,fieldset,legend,input,button,textarea,p,blockquote,th,td {    margin: 0;    padding: 0;}table {    border-collapse: collapse;    border-spacing: 0;}fieldset,img {    border: 0;}address,caption,cite,code,dfn,em,strong,th,var,optgroup {    font-style: inherit;    font-weight: inherit;}del,ins {    text-decoration: none;}li {    list-style: none;}caption,th {    text-align: left;}h1,h2,h3,h4,h5,h6 {    font-size: 100%;    font-weight: normal;}q:before,q:after {    content: '';}abbr,acronym {    border: 0;    font-variant: normal;}sup {    vertical-align: baseline;}sub {    vertical-align: baseline;}legend {    color: #000;}input,button,textarea,select,optgroup,option {    font-family: inherit;    font-size: inherit;    font-style: inherit;    font-weight: inherit;}input,button,textarea,select {    *font-size: 100%;}This will reset all main selectors to their defaults, removing any obtrusive styling.