Moles: Moles, also known as nevi, are skin-colored, brown or black, can be large or small, raised or flat, and appear anywhere on the body. Almost everyone has at least a few moles. Some people have 100 or more. Moles that are present at birth are considered a type of birthmark. Moles also can develop in childhood or adolescence. These are not considered birthmarks. Some fade away after many years. Moles usually don't cause problems. However, they occasionally can become cancerous, so you should watch them and see a dermatologist if a mole changes in color, size or shape or if an unusual-looking new mole appears. Moles that are present at birth, called congenital nevi, may be more likely than others to someday become cancerous. For more information about skin cancer, visit SkinCancerNet and the ABCDEs of Melanoma Detection.
Café-au-lait spots: In fair-skinned people, these spots often are oval-shaped and light brown, like the color of café-au-lait, which is French for "coffee with milk." In dark-skinned people, they are the color of black coffee. Café-au-lait spots usually aren't a problem and may fade over time, though they probably won't go away completely. A number of them grouped together might mean that there are other health problems, such as a rare genetic nervous system disorder called neurofibromatosis, which causes benign tumors to grow on the nerves. (Usually there are other indications of this disorder, such as growths on the eye and abnormal development of the spine.) 
Mongolian spots: These marks are flat, vary in color from light blue to dark blue to blue-gray, and often appear on babies' backs or buttocks. Sometimes they look like bruises. They're most common in babies with darker skin and usually, although not always, go away after a few years.
Macular stains, or salmon patches: These are the most common types of vascular birthmarks and are known as "angel's kisses" (when they appear on the forehead, eyelids, nose or upper lip) or "stork bites" (when they're on the back of the neck). They usually are small, flat, and red or pink. Macular stains may go away within a few years of birth, or last until adulthood. They don't cause problems and don't need to be treated.
Hemangiomas: There are two types of hemangiomas: superficial (strawberry) and deep (cavernous). Both can be small or large. The blood vessels that cause superficial hemangiomas are close to the top layer of the skin, so these birthmarks are vibrant strawberry red. Deep hemangiomas are bluish-purple because the abnormal blood vessels are deeper in the skin. Deep hemangiomas usually don't show up until after birth and then may alarm parents when they grow larger and bulge in the first six to nine months of life. Most of these marks usually start shrinking and fading after the child is a year old, and they are gone by age 5 in half of children. Ninety percent of hemangiomas are gone by age 10. After they clear up, they might leave a light mark or rough-feeling skin. 
Port-wine stains: Named after the maroon-colored wine, port-wine stains also can be pink or red. They appear at birth, often on the face or head, but sometimes on other parts of the body, and may beflat or bumpy. Port-wine stains grow as the child grows, and they do not go away on their own. Over time, they become thicker and develop a darker red to deep purple color. In adulthood, they may develop bumps or nodules that can bleed. Although rare, some people with port-wine stains have health conditions, such as Sturge-Weber and Klippel-Trenaunay-Weber syndromes, in which blood vessels don't form correctly. Children with port-wine stain birthmarks should be evaluated by a dermatologist.Photo references:
Moles, Cafe-au-lait spots, Mongolian spots, and Hemangiomas: Photos used with permission of the American Academy of Dermatology National Library of Dermatologic Teaching Slides.
Salmon patch: This photo was previously published in the Journal of the American Academy of Dermatology, 2008 Dec: 59(6): 1077-79. Happle R. “What is a capillary malformation?” Copyright Elsevier (2008).
Port wine stain: This photo was previously published in Dermatology DDxDeck, Vol 1, Pg 141. Habif T. Campbell J. Chapman M et al. “Vascular malformations.” Copyright Elsevier (2006).
