Mejor Respuesta - Seleccionada por quien preguntó.The sentence is written in the past simple tense using passive voice.
Navigation to the webpage "was" canceled.
The past simple passive without the use of the word "by" expresses the minimun amount of information about the situation.
By using the simple present passive voice here the idea is that:
-the action happened in the past
-that no action is taking place
-a certain state or situation exists
Using the present perfect passive voice:
Navigation to the webpage "has been" cancelled..
The present perfect passive allows for subtle differences in meaning because it is connected to the "present" tense form of the verb have: "has".
This may indicate that.
-the action happened in an indefinite past up to "now"
-the action is repetitive (perhaps cancelled according to a schedule)
-the action is pending (further action may be taken)
In the simple past passive the past participle functions like an adjective when the word "by" is not used. The situation is static. If there is a specific mention of time then the simple form is used.
Navigation to the webpage was canceled on Wednesday.
In the present perfect the action is more indefinite which is why adverbs like frequently,ever, just,already, still, etc. are often used in the present perfect in order to explain the situation.
Navigation to the webpage has frequently been canceled.
Navigation to the webpage has just been cancelled.
Navigation the the webpage has already been cancelled.
Hope this helps !
:)