Click the 
Actions button on the corresponding sheet tab.
In the drop-down list select the Delete item. The sheet will be deleted.
To delete a sheet:
Click the Actions button on the corresponding sheet tab.
In the drop-down list select the Delete item. The sheet will be deleted.
When a sheet is deleted, the formulas referring to this sheet are automatically adjusted. For example, the formula "=B0+1+"Sheet2"!A0 after the Sheet2 is deleted looks as follows: "=B0+1+#LINK!A0".
See also:
Adding a New Sheet and Working with It