There are blunders commonly taken by graphic designers or novices in graphic design which crucially affect output.
The impact of visual design is sometimes ignored. Each screen and everything on the screen must contribute to the over-all significance of the design. Lack of unity weakens the whole presentation. It is best to use the grid structure to make the page design easy to understand and even speed-read through. If graphics do not match, they do not contribute to learning or appeal to the senses. When using illustrations or clip arts, they should be both visually engaging and impact on learning. Confusing use of contrast will also distract and weaken or confuse the communication thrust.
Utilise the appropriate contrast in terms of fonts and colours to bring out exactly what you want to relay. Misuse of fonts could mean using too many fonts, or not using the correct type (easy to read) and size. Fonts should be the correct type and size in order to relay the correct message and reach the desired audience.
Knowing what these slip-ups are and being vigilant in order not to commit these are some of the challenges in graphic design.