CSS - Modifying the file but changes not displayed

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I'm a newbie with CSS, so please bear with me.  I downloaded the CSS file that is in effect from the Resource Manager.  I saved it a .txt file and made some changes to the fonts.  Then, I renamed it as a .css and uploaded back to the Resource Manager.  The Resource Manager automatically appends a number to the filename because the original file is still there.  So, I deleted the orginal .css file in the Resource Manger and then renamed the one I just uploaded (deleted the appended number).  So, everything looks ok with the filename in the Resource