* The number of D's: One or two D's in a sea of A's and B's might be overlooked, especially if there's a clear explanation (e.g., a temporary family crisis). Many D's, however, will significantly hurt your chances.
* The context of the D's: A D in a difficult, highly competitive course might be viewed differently than a D in an easier elective. Colleges look at the rigor of your course load.
* The rest of your application: A strong application with compelling extracurricular activities, impressive essays, and strong letters of recommendation can sometimes compensate for a few lower grades. Colleges consider the whole applicant, not just the GPA.
* The type of college: Highly selective colleges are much less likely to accept an applicant with several D's than less selective colleges or community colleges.
* The reason for the D's: Colleges often want to understand the circumstances behind poor grades. A well-explained reason (such as a documented illness or family emergency) can mitigate the negative impact.
In short, while a single D might not be a deal-breaker, multiple D's significantly reduce your chances of admission to a competitive college. It's much better to strive for higher grades throughout high school. If you're concerned about your grades, talk to your guidance counselor; they can provide valuable advice and support.