Creationists often present "mined quotes" which, when taken out of context, appear to undercut evolution, or quotes which have been altered so that it appears as though the source of the quotation opposes evolution when this is not true. Let's start with a classic.
Darwin on the eye
A typical example of quote mining is taken from The Origin of Species by Charles Darwin in which he considers the evolution of the eye:
To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree.
– The Origin of Species, 1st Edition, Chapter 6, pp. 186-7
This quote is clearly taken out of context because Darwin continues:
Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real. How a nerve comes to be sensitive to light, hardly concerns us more than how life itself first originated; but I may remark that several facts make me suspect that any sensitive nerve may be rendered sensitive to light, and likewise to those coarser vibrations of the air which produce sound.
In this case, the originally quoted sentence is clearly a rhetorical device: Darwin is first admitting to the 'seeming' strength of a criticism in order to better refute it. Darwin, in fact, goes on to devote three further pages to this subject, all of them arguing as to why he believes the original objection to be unwarranted. Thus, presenting the original sentence alone gives the reader a false impression of what Darwin thinks about the subject: that he thinks a problem is unsolvable, when in fact in context he was merely admitting that it might seem unsolvable, at first.
Not all creationists stoop to this level but there is a lot of it about. We will bring you another quote mine special next time on "Down the Quote Mine".