At the end of staining, tissue sections must be fully dehydrated by alcohol before applying Cytoseal. If you rush the process and leave water mixed with the alcohol and glue, the tissue will have strange dark flecks in it. Notice how the tissue in the far lower right corner of this picture is not contaminated as much. The cytoseal was probably dropped directly on that area of tissue.
You will also notice what looks like streams of bubbles. Since cytoseal is toluene-based and toluene is insoluble in water, any water left on the slide will create this cloudy mess of bubbles.
Solution: Recoverslip. Slide off the coverslip. Give the slide a few good swishes in the alcohol, a few drops of glue, and a brand new coverslip.
