personalizing external style sheets

[bartonlewis]

This is a general question on how external css stylesheets can be modified according to an individual's needs.  I found code for using a magnifier lens here http://www.cs.northwestern.edu/~riesbeck/demo/magnifier_v3/magnifier.html.  This was helpful as I do not know javascript and had difficulty finding code for a magnifier that worked on more than one image.  I love this effect but I don't know how to modify the presentation of my images while taking advantage of it.  I want images centered, in a gallery with margins between each div etc.  When you are using the css from an external stylesheet that is not your own, how do you incorporate your own stylistic preferences for your content? 

[dsonesuk]

Create your own custom stylesheet and make sure it is below the link of any other stylesheet. Any amendments to styling of previous stylesheets coding will now be overridden by this custom stylesheet. This has the added benefit in that you won't be amending current css stylesheets, which may result in a possible mistake happening and losing or being unable to identify where you made the error, you will be only editing your custom css to override the current .

[bartonlewis]

Thank you for your reply.  Before I test this, I am unable to get my html to display properly uploaded to my server referencing the external css, though it does so on Brackets' Live Preview.  But I believe that is a query for another post, so I have posted about this problem separately.