Writing style and writing voice are often confused. A writers voice is that ineffable quality of their writing that flows naturally from the writer. Style on the other hand is a series of choices and while a writer may have a preferred style this is something that he must consider for each piece that he creates, just as a painter must choose the paint, brushes and theme of his work.
The first style choice that a writer must make is typically narration. In non-fiction this is largely a decision made by the publisher. Most do not want articles written from the first person point of view so a writer should write with that style choice in mind. In fiction it is more difficult. A story from the first person, where the character is explaining what happened himself is going to feel very different stylistically than the third person narration. Other style choices in narration are the unreliable narrator in which the story is told by someone who is wrong or lying, and the omniscient narrator, a narrator who knows every thought and feeling of every character as well as the entire story.
Many of the rules of writing also cover style choices, and though the advice typically falls on one side of the style choice these are decisions that a good writer must make on an individual basis. One of the most common of these pieces of advice is "show, don't tell". This is something that is typically true but the best writers know when the best choice of style is to tell the reader what they need to know and move on. This is a similar problem when dealing with the amount of detail to put into a scene. These choices are often made easier by the type of story or article. The shorter it is the less detail should be included.
Finally, there are style choices designed to set mood. These are often the most important. The same scene written for a horror book will have a very differ style than one written for a romance. These changes can and often should be subtle. You don't need to put the horror game in the middle of the night, instead chose a few words differently. Horror typically has more description on location while a romance would describe the people more carefully. This can also be an excellent way to ramp up the tension towards the end of a story by shorting the length of sentences. Short sentences are faster than long sentences.
Learning to choose the correct style for your articles and stories is something that you may never have to think about it but by spending a few minutes considering the best choices for the style will help you considerably in creating the best possible work.