Avoid WYSIWYG Mistakes
Very often you will want to set up experiments that will run across a set of similar pages like all the product pages in an e-commerce shop. You do that by picking one product page and build the experiment on that one. Let's say that's a product that costs $99.
The tested change is a color change of the pricing display. That change can be done in several ways but the two "dangerous" ones are Edit > Edit HTML and Edit > Edit WYSIWYG. If using any of the two, the original content will be REPLACED by the new content (the price with the new color). Therefore, on all pages where the experiment will be executed the price will be replaced with the same price of the product where the test was set up initially.
Whenever changing dynamic elements DO NOT use any of the two options inside Visual Editor: Edit > Edit HTML and Edit > Edit WYSIWYG. Any other option is safe to use.
That being said, the color of a price on a product page can be easily changed by using the Edit CSS function without any side effect.