Each text has its own peculiarities, but there are a number of well-known scanning errors you will be dealing with all the time.
Punctuation is always a problem. Periods, commas and semi-colons are often confused, as are colons and semi-colons. There are also usually a number of extra or missing spaces in the e-text.
The problem of quotes can assume nightmarish proportions in a text which contains a lot of dialog, particularly when single and double quotes are nested.
The numeral 1, the lower-case letter l, the exclamation mark ! and the capital I are routinely confused, and often, single or double quotes may be mistaken for one of these.
Lower-case m is often mistaken for rn or ni.
The letters h and b and e and c are commonly mis-read, and these are probably the hardest of all to catch, since ear/car, eat/cat, he/be, hear/bear, heard/beard are all common words which no spell-checker will flag as problems.
" Hello1' caIled jirnmy breczily. 11Anyone home ? " There seemed to he no-oneabout. Only tbe eat beard him."
"Hello!" called Jimmy breezily, "Anyone home?" There seemed to be no-one about. Only the cat heard him.