These tuples are used in line 253, to verify the pair of tag and attribute. For example, **icon** attribute of **command** tag is url-valued, but i'm not sure if is this true for all other tags.

If we don't need this verification, we could simple change **href|src** in the regular expression to **profile|src|classid|poster|formaction|longdesc|codebase|href|background|usemap|action|manifest|data|cite|icon**.