When designing webpages I run into issues with designing for multiple size pages for different phones, tablets and desktop monitors. One time I had an issue with a laptop being so old that the resolution was lower than expected by a small amount, 100 pixels, and that caused issues with a simple design. But, with this browser I could load a page and specify over five sizes all in one browser window. The browser has error checking built in as well as hints that can correct the code for you in CSS. Also, if you have an issue it has a chat built into it. The price is free at first but about $9.00 per month for individuals billed yearly and $39.00 a month for teams up to ten.