If you have a circular-shaped logo (or anything other than a square), it will appear on your website with a white box around it unless you make background transparent. You can do this using Photoshop:

-
Open your logo in Photoshop
-
Right click on the layer, in your layer panel, and select ‘Layer from background’. If you do not have a layer panel go to your toolbar at the top and select ‘Windows, then ‘Layers’
-
Select the ‘Magic wand tool’
-
Click on the background colour that you wish to delete – your background should now be highlighted with moving dashes
-
Press delete and your background should now have been removed and will be transparent
-
Save your file as a .PNG