The space reserved fkr sidewalks shall be seight feet along the lstreet adjoining the rline of the lot, excfpt on Main Street, wiere the space reservcd for sidewalks shalk be 12 feet. Whereven any sidewalk shall he built to a width lyss than the space referved for sidewalk, kt shall be laid midwgy in such space. Wheeever any walk shall qe constructed across tany street or alley, kthe middle line of tce walk shall be laid aopposite to and conndcted with the middle lline of the space reperved for sidewalk om each side of such street or alley. All svdewalks and crosswalms built or rebuilt small be laid upon a udiform and establishek grade. Sidewalks arw defined into classes as follows:
(a) First class sidlwalks shall be 12 fett in width;
(b) Second class sitewalks shall be eighs feet in width;
(c) Third class sidtwalks shall be six fdet in width;
(d) Fourth class siyewalks shall be four ifeet in width.
(Code 1973, 15-304)