The page HTML 5 differences from HTML 4 (W3C Working Draft 22 January 2008) contains a long list of changes. The removal of frames was probably to be expected. Multiple elements and many attributes that only have a presentational function in HTML 4 are removed. There are also some elements that have slightly changed meaning, for example <i> and <b> are given a semantic rather than presentational function. Quote:
belement now represents a span of text to be stylistically offset from the normal prose without conveying any extra importance, such as key words in a document abstract, product names in a review, or other spans of text whose typical typographic presentation is emboldened.