Spelling and Grammar
The problems associated with bad spelling and grammar are obvious: they seriously interfere with the reader’s understanding of the text. Usually, the reader can take a guess at the intended meaning, but that shouldn’t be counted on. As well, if the grammar and spelling are sloppy, your reader will assume your research is also sloppy and they won’t take you seriously.
If you’re writing on a computer, don’t rely on the spell-checker or grammar-checker to do the work for you. The English spelling and grammar rules are too flexible, too fickle, for a machine to come up with a correct answer all the time. Do have a look at the suggestions made, though, as well as looking for those the computer may have missed.