Necesito ayuda con página web errores validación

soy nuevo en esto de “programar” y estoy creando una página web,tengo muy poquitos conocimientos,(los estoy adquiriendo poco a poco,llevo menos de una semana),pues bien tengo problemas a la hora de validar mi web en dreamweaver tengo muuuchos errores y no se por donde empezar… si alguien puede ayudarme os agradecería muchisimo vuestra colaboración…,os adjunto los errores

|||  Gravedad     Archivo     Descripción     Línea     |||  Error Bogus doctype.     1    Error Quirky doctype. Expected <!DOCTYPE html> .     1    Error Bad value cleartype for attribute http-equiv on element meta .     57   Error Bad value https://fonts.googleapis.com/css?family=Roboto:100,300,400,500,600,700|Material+Icons for attribute href on element link : Illegal character in query: | is not allowed.     79   Error A link element with an as attribute must have a rel attribute that contains the value preload .    79   Error Stray end tag div .    85   Error Start tag a seen but an element of the same type was already open.     159      Error An img element must have an alt attribute, except under certain conditions. For details, consult guidance on providing text alternatives for images .      159      Error Stray end tag img .    159      Error Stray end tag a .      160      Error A slash was not immediately followed by > .    172      Error End tag had attributes.    172      Error Stray end tag span< .      172      Error End tag div seen, but there were open elements.    173      Error Unclosed element span .    172      Error End tag nav seen, but there were open elements.    175      Error Unclosed element div .     170      Error No p element in scope but a p end tag seen.    206      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    299      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    300      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    301      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    304      Error CSS: color : #white is not a valid color 3 or 6 hexadecimals numbers.      304      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    305      Error Duplicate attribute style .    308      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    308      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    309      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    312      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    313      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    316      Error Element li not allowed as child of element div in this context. (Suppressing further errors from this subtree.)    317      Error Stray end tag ul .     319      Error End tag div seen, but there were open elements.    320      Error Unclosed element span .    318      Error No li element in scope but a li end tag seen.      321      Error Stray end tag ul .     322      Error Stray end tag div .    327      Error Start tag a seen but an element of the same type was already open.     334      Error Stray end tag a .      350      Error Stray end tag a .      352      Error Stray end tag a .      353      Error Stray end tag a .      356