What is the mean of 'samma ditti' in Ariya-Ashtanga Marga?

A full description and meaning of that Samma Ditthi in the Ariya-Ashtanga Marga is given in the Samma,ditthi Sutta. Giving a full description of this here will be too long for this format.

The morality aspect of the path is mainly based on abstaining from certain unwholesome conduct.

Right Effort is more in lines of developing wholesome mental habits which subdue the 5 hindrances, development of the Seven Factors of Enlightenment.

Another aspect of Sammadhitthi is described in Maha-salayatanika Sutta MN 149.

.."However, knowing & seeing the eye as it actually is present, knowing & seeing forms... consciousness at the eye... contact at the eye as they actually are present, knowing & seeing whatever arises conditioned through contact at the eye — experienced as pleasure, pain, or neither-pleasure-nor-pain — as it actually is present, one is not infatuated with the eye... forms... consciousness at the eye... contact at the eye... whatever arises conditioned by contact at the eye and is experienced as pleasure, pain, or neither-pleasure-nor-pain.

"For him — uninfatuated, unattached, unconfused, remaining focused on their drawbacks — the five clinging-aggregates head toward future diminution. The craving that makes for further becoming — accompanied by passion & delight, relishing now this & now that — is abandoned by him. His bodily disturbances & mental disturbances are abandoned. His bodily torments & mental torments are abandoned. His bodily distresses & mental distresses are abandoned. He is sensitive both to ease of body & ease of awareness.

"Any view belonging to one who has come to be like this is his right view. Any resolve, his right resolve. Any effort, his right effort. Any mindfulness, his right mindfulness. Any concentration, his right concentration: just as earlier his actions, speech, & livelihood were already well-purified. Thus for him, having thus developed the noble eightfold path, the four frames of reference go to the culmination of their development. The four right exertions... the four bases of power... the five faculties... the five strengths... the seven factors for Awakening go to the culmination of their development.1 [And] for him these two qualities occur in tandem: tranquillity & insight....

Samma Ditthi is in short Right understanding. Right understanding is explained as the knowledge of the four noble truths. In other words, it is the understanding of oneself as one really is, because, as the Rohitassa Sutta states, these truths are concerned with the "one-fathom long body of man." The key-note of Buddhism is this right understanding.

Consider the following statement: Pemato jayati soko, pemato jayati bhayam. [From affection springs grief, from affection springs fear]. Conventional minds will recoil to the idea - as it indeed did when the Buddha said it. The truth and meaning of Dhamma becomes a private experience by the wise only when there is insight or vipassana. But vipassana depends on samadhi or concentration. And samadhi depends on Samma-ditthi. Thus, everything in Dhamma is connected. Why is that? The Buddha is speaking, albeit in diverse ways, only of one thing and one thing alone – dukkha and the cessation of dukkha.

One pre-requisite of one coming to ‘Right View’ (Samma Ditti) is learning to welcome advice of the Supreme Buddha with delight. We must not treat even a single verse of Dhamma as being plain and simple. We must learn to treat the Noble Dhamma as supreme. We must consider this Dhamma to be the most profound. One would ask as to why should we learn to perceive it in that way? It is because this Noble Dhamma is Svākkhāto (it is well proclaimed). Nothing needs to be corrected in this Dhamma and nothing can be discarded on the basis that it is too plain and simple (if one understands this quality, then this person comes to Samma Ditti— right view). This is why we must hold dear the advice we receive and use that noble advice to discipline ourselves than vice-a-versa.

In its fullest measure right view involves a correct understanding of the entire Dhamma or teaching of the Buddha, and thus its scope is equal to the range of the Dhamma itself. But for practical purposes two kinds of right view stand out as primary. One is mundane right view, right view which operates within the confines of the world. The other is supramundane right view, the superior right view which leads to liberation from the world.

Mundane right view involves a correct grasp of the law of kamma, the moral efficacy of action. Its literal name is "right view of the ownership of action", and it finds its standard formulation in the statement: "Beings are the owners of their actions, the heirs of their actions; they spring from their actions, are bound to their actions, and are supported by their actions. Whatever deeds they do, good or bad, of those they shall be heirs."

This superior right view leading to liberation is the understanding of the Four Noble Truths. It is this right view that figures as the first factor of the Noble Eightfold Path in the proper sense: as the noble right view. Thus the Buddha defines the path factor of right view expressly in terms of the four truths: "What now is right view? It is understanding of suffering (dukkha), understanding of the origin of suffering, understanding of the cessation of suffering, understanding of the way leading to the cessation to suffering."

If a virtuous person were to constantly reflect and expand upon even one strand mentioned in the Samma Ditti sutta referred by Suminda above, it will be for his long term benefit.

For example one can take the section on the four types of Food and constantly reflect on that reality and confirm that view.

Mr. Piya Tan has written an in depth commentary of the Samma Ditti sutta here.

http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2009/12/11.14-Sammaditthi-S-m9-piya.pdf